Best SIM cards for travelling in Thailand

Contents

In this guide:

Get a Thailand SIM card
Buying a Thailand eSIM
Roaming in Thailand with your telco
Use free public WiFi in Thailand
SIM cards for travelling in Thailand FAQs

From incredible street food to its famous temples, Thailand is a popular international destination for Aussie travellers. If you're headed over to Bangkok, Chiang Mai, or Phuket and want to stay connected then you'll want to check out one of these affordable mobile roaming plans.

Before we start, here are the cheapest roaming plans from each postpaid telco featured in this guide:

#1	Tangerine Telecom	Tangerine Telecom 12GB Mobile SIM 12GB data at download speeds up to 100Mbps Uses part of the Telstra 4G Mobile Network Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $23/mth Min. cost $23 Go to Site	$23/mth Min. cost $23	Go to Site
#2	Belong	Belong 25GB Mobile Plan 25GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks $30/mth Min. cost $30 Go to Site	$30/mth Min. cost $30	Go to Site
#3	Vodafone	Vodafone $49 Small Plan 100GB data Vodafone 5G Network in selected areas with 5G devices Deal: Get 100GB for $39 (incl. 50GB bonus + $10/mth off) on the $49 Small plan. T&Cs apply. $39/mth Min. cost $39 Go to Site	$39/mth Min. cost $39	Go to Site
#4	Optus	Optus $55 Optus Choice Plus Plan 50GB data Optus 5G in selected areas (exc NT) with a 5G device $55/mth Min. cost $55 Go to Site	$55/mth Min. cost $55	Go to Site
#5	Telstra	Telstra $65 Basic Upfront Mobile Plan 50GB data Telstra 5G Network in selected areas with 5G devices Deal: Get your first 3 months device protect on Telstra, then $10/mth. $65/mth Min. cost $65 Link not supplied	$65/mth Min. cost $65	Link not supplied

Plus, here are the cheapest roaming plans with at least 28-day expiry from each prepaid telco featured:

UNLIMITED 10GB Plan

10GB data at download speeds up to 100Mbps
On the Optus 4G Plus Mobile Network

$22

Per 28 Day Renewal

Link not supplied

$22

Per 28 Day Renewal

Link not supplied

felix 25GB Mobile Plan

25GB data at download speeds up to 150Mbps
Vodafone 5G Network in selected areas with 5G devices
Deal: Get 50% off your first 3 mths when you switch to felix. $12.50/mth for first 3 mths, then $25/mth. Use promo code FELIX50. T&Cs apply

$25

Per 1 Month Renewal

Go to Site

$25

Per 1 Month Renewal

Go to Site

$26 Prepaid

17GB data at download speeds up to 150Mbps
Telstra 5G Network in selected areas with 5G devices
Deal: Get 17GB data for the first 3 recharges, then 7GB from 4th recharge. New customers only. Activate by 07.07.25

$26

Per 28 Day Renewal

Go to Site

$26

Per 28 Day Renewal

Go to Site

Travelling with eSIM: Everything you need to know

Need a mobile plan overseas? Consider a travel eSIMs instead of international roaming.

Get a Thailand SIM card

Travelling for more than a week? It might be worth it to get a local Thailand SIM card.

There are a couple of things to keep in mind when buying a SIM card in Thailand:

Double-check your mobile isn't locked to a network. In general most smartphones these days aren't locked so you can readily switch to any SIM-only plan.
Check the terms and conditions. Make sure you're not signing up for a contract that's going to last longer than your holiday and that you can turn off auto-renewal.

The easiest way to pick up a Thailand SIM card is at one of the following airports when you arrive:

Suvarnabhumi Airport (Bangkok International Airport – BKK)
Don Mueang International Airport (DMK)
Phuket International Airport (HKT)
Chiang Mai International Airport (CNX)
Krabi International Airport (KBV)

Remember you may need ID in order to make your purchase. The big three mobile operators in Thailand are AIS, True Move and DTAC. DTAC offers "Tourist" SIMS from 449 baht (AUD$18.50 at the time of writing). This includes unlimited calls to local numbers and unlimited data with an 8-day expiry.

Buying a Thailand eSIM

If your mobile has eSIM then it can be a good option instead of international roaming when you're taking a trip to Thailand. All you need to do is buy and set up your Thailand eSIM before you depart or when you arrive.

Airalo is one of our top picks for Thailand travel eSIMs. Here are Airalo's Thailand plan prices:

Price	Inclusions	Expiry
USD$9.90	100 mins, 50GB	10 days	View on Airalo
USD$19.95	Unlimited calls and texts, unlimited data	15 days	View on Airalo

Other providers include eSIM Thailand where plans start from USD$9.99 for 50GB of data with 10-day expiry. There are also unlimited data plans from as little as USD$12.99 with an eight-day expiry.

You can even customise an eSIM with a daily amount starting from USD$2.99 for 2GB. See eSIM Thailand's pricing here:

Plan	Price	Inclusions	Expiry
Unlimited with calls	USD$12.99	Unlimited local calls, unlimited data	Eight-days	View on eSIM Thailand
50GB with Calls	USD$9.99	Unlimited local calls, 50GB data	10-days	View on eSIM Thailand
Daily Data	USD$2.99	2GB	One day	View on eSIM Thailand

Roaming in Thailand with your telco

Roaming in Thailand with felix

felix is a Vodafone MVNO with a decent roaming offer. For $20 you get 4GB of data, 100 text messages and 100 minutes of calls. It has a 365-day expiry so you don't need to use all your roaming inclusions at once.

Here are felix's mobile plans that you can activate roaming on:

#1	felix mobile	felix mobile felix 25GB Mobile Plan 25GB data at download speeds up to 150Mbps Vodafone 5G Network in selected areas with 5G devices Deal: Get 50% off your first 3 mths when you switch to felix. $12.50/mth for first 3 mths, then $25/mth. Use promo code FELIX50. T&Cs apply $25 Per 1 Month Renewal Go to Site	$25 Per 1 Month Renewal	Go to Site
#2	felix mobile	felix mobile felix 50GB Mobile Plan 50GB data at download speeds up to 150Mbps Vodafone 5G Network in selected areas with 5G devices Deal: Get 50% off your first 3 mths when you switch to felix. $15/mth for first 3 mths, then $30/mth. Use promo code FELIX50. T&Cs apply $30 Per 1 Month Renewal Go to Site	$30 Per 1 Month Renewal	Go to Site
#3	felix mobile	felix mobile felix Unlimited Mobile Plan Unlimited data at download speeds up to 20Mbps Vodafone 5G Network in selected areas with 5G devices Deal: Get 50% off your first 3 mths when you switch to felix. $20/mth for first 3 mths, then $40/mth. Use promo code FELIX50. T&Cs apply $40 Per 1 Month Renewal Go to Site	$40 Per 1 Month Renewal	Go to Site

Roaming in Thailand with Vodafone

Fortunately Vodafone's famous $5 roaming postpaid plan add-on is available in Thailand. For just $5 a day you get full access to your full plan inclusions.

Vodafone's $5 roaming is available for up to 90 days each year. You can activate $5 roaming on any of these Vodafone postpaid plans:

#1	Vodafone	Vodafone $49 Small SIM Only Plan 100GB data Vodafone 5G Network in selected areas with 5G devices Deal: Get 100GB for $39 (incl. 50GB bonus + $10/mth off) on the $49 Small plan. T&Cs apply. $39/mth Min. cost $39 Go to Site	$39/mth Min. cost $39	Go to Site
#2	Vodafone	Vodafone $59 Medium SIM Only Plan 360GB data Vodafone 5G Network in selected areas with 5G devices Deal: Get 360GB for $49 (incl. 180GB bonus + $10/mth off) on the $59 Medium plan. T&Cs apply. $49/mth Min. cost $49 Go to Site	$49/mth Min. cost $49	Go to Site
#3	Vodafone	Vodafone $69 Large SIM Only Plan 720GB data Vodafone 5G Network in selected areas with 5G devices Deal: Get 720GB for $59 (incl. 360GB bonus + $10/mth off) on the $69 Large plan. T&Cs apply. $59/mth Min. cost $59 Go to Site	$59/mth Min. cost $59	Go to Site

If you're a Vodafone prepaid customer, you can't access $5 roaming. Instead you can choose one between these three add-ons:

Pack	Price	Inclusions
1-day expiry	$5	25 mins, 30 texts, 200MB
7-day expiry	$15	90 mins, 120 texts, 750MB
14-day expiry	$35	200 mins, 300 texts, 2GB

Roaming in Thailand with Optus

Just like Vodafone, Optus offers roaming on postpaid plans from $5. Unlike Vodafone, you don't get access to your full plan. Instead, you get 5GB each day and unlimited talk and text. Any inclusions you don't use expire at the end of each day and if you go over the data allowance you'll be charged again.

You can access Optus roaming in any country Optus designates as Zone 1 including Thailand.

Optus' $5 roaming is available on the following postpaid plans:

#1	Optus	Optus $55 Optus Choice Plus Plan 50GB data Optus 5G in selected areas (exc NT) with a 5G device $55/mth Min. cost $55 Go to Site	$55/mth Min. cost $55	Go to Site
#2	Optus	Optus $65 Optus Choice Plus Plan 200GB data Optus 5G in selected areas (exc NT) with a 5G device $65/mth Min. cost $65 Go to Site	$65/mth Min. cost $65	Go to Site
#3	Optus	Optus $79 Optus Promo Plan 360GB data Optus 5G in selected areas (exc NT) with a 5G device Deal: Get up to $10/mth SubHub credit to use on your favourite subscriptions for 12 months. T&Cs apply. $69/mth Min. cost $69 Go to Site	$69/mth Min. cost $69	Go to Site
#4	Optus	Optus $85 Optus Choice Plus Plan 400GB data Optus 5G in selected areas (exc NT) with a 5G device SubHub: Receive up to $20/mth SubHub credit when you have an active SubHub account with subs greater than $0. T&Cs apply $85/mth Min. cost $85 Go to Site	$85/mth Min. cost $85	Go to Site

Optus also has a few options for its prepaid customers including:

Add-on	Price	Inclusions
1-day expiry	$5	100 mins, 100 texts, 1GB
7-day expiry	$35	700 mins, 700 texts, 7GB

Roaming in Thailand with Circles.Life

Circles-Life is another Optus MVNO with roaming add-ons. Circles has two options, a single-day expiry that gives you 1GB of data for $15, or a monthly expiry option with 5GB of data for $30. The monthly option is fairly decent compared to other offers in the market given the monthly expiry.

The monthly roaming add-on renews automatically so you'll need to disable it when you come home. The daily add-on will auto-renew while you're overseas but you'll stop being charged in Australia.

You can add either roaming pack to the following Circles.Life plans:

#1	amaysim	amaysim UNLIMITED 32GB Plan 50GB data at download speeds up to 100Mbps Optus 5G in selected areas with 5G devices ex. NT Deal: Save $20 & includes 18GB bonus data for first renewal when you sign up by 30.04.25. Online only. T&Cs apply $10 Starter Pack 28 Day Expiry Link not supplied	$10 Starter Pack 28 Day Expiry	Link not supplied
#2	amaysim	amaysim 7-day UNLIMITED 10GB Plan 10GB data at download speeds up to 100Mbps Optus 5G in selected areas with 5G devices ex. NT $10 Per 7 Day Renewal Link not supplied	$10 Per 7 Day Renewal	Link not supplied
#3	Coles Mobile	Coles Mobile Prepaid $30 for 28 Days - Starter Pack 32GB data On the Optus 4G Plus Mobile Network Deal: Get 32GB for $11 (incl. $19 off first renewal). Offer ends 29.04.25. T&Cs apply. $11 Starter Pack 28 Day Expiry Link not supplied	$11 Starter Pack 28 Day Expiry	Link not supplied
#4	Optus	Optus Optus Prepaid $12 SIM 5GB Speed capped at 150Mbps Optus 5G in selected areas (exc NT) with a 5G device Deal: 5GB data on first 3 recharges, 3GB standard data thereafter. New services only. Speed caps apply. T&Cs apply $12 Per 7 Day Renewal Go to Site	$12 Per 7 Day Renewal	Go to Site
#5	Optus	Optus Optus Prepaid $12 SIM 5GB Speed capped at 150Mbps Optus 5G in selected areas (exc NT) with a 5G device Deal: 5GB data on first 3 recharges, 3GB standard data thereafter. New services only. Speed caps apply. T&Cs apply $12 Starter Pack 7 Day Expiry Go to Site	$12 Starter Pack 7 Day Expiry	Go to Site
#6	Moose Mobile	Moose Mobile Moose 26.80 SIM Only 40GB data at download speeds up to 100Mbps On the Optus 5G Mobile Network Deal: Get 40GB for $12.40 – Includes $14.40 off and 13GB bonus data for first 6 months. Offer ends 31.05.25 $12.40/mth Min. cost $12.40 Link not supplied	$12.40/mth Min. cost $12.40	Link not supplied
#7	iiNet	iiNet 25GB Small Plan 25GB data at download speeds up to 150Mbps On the Vodafone 4G Mobile Network Deal: 50% off - $12.50/mth for first 6 months, then $25/mth ongoing. Available until withdrawn. T&Cs apply. $12.50 Per 1 Month Renewal Go to Site	$12.50 Per 1 Month Renewal	Go to Site
#8	TPG	TPG 25GB Small Plan 25GB data at download speeds up to 150Mbps On the Vodafone 4G Mobile Network Deal: 50% off - $12.50/mth for first 6 months, then $25/mth ongoing. Available until withdrawn. T&Cs apply. $12.50 Per 1 Month Renewal Go to Site	$12.50 Per 1 Month Renewal	Go to Site
#9	Boost Mobile	Boost Mobile $13 Prepaid 7GB data at download speeds up to 150Mbps Telstra 5G Network in selected areas with 5G devices Deal: Get 7GB data for the first 3 recharges, then 5GB from 4th recharge. New customers only. Activate by 07.07.25 $13 Per 7 Day Renewal Go to Site	$13 Per 7 Day Renewal	Go to Site
#10	Telstra	Telstra $13 Pre-Paid Mobile SIM Starter Kit 3GB data at download speeds up to 150Mbps Telstra 5G Network in selected areas with 5G devices $13 Starter Pack 7 Day Expiry Link not supplied	$13 Starter Pack 7 Day Expiry	Link not supplied

Roaming in Thailand with Tangerine

Tangerine is a Telstra MVNO with two fairly priced roaming add-ons:

Pack	Price	Inclusions
Three-day expiry	$60	300 mins, 300 texts, 3GB
Seven-day expiry	$35	30 mins, 30 texts, 5GB
14-day expiry	$55	60 mins, 60 texts, 10GB

Here are Tangerine's mobile plans:

#1	Tangerine Telecom	Tangerine Telecom 12GB Mobile SIM 12GB data at download speeds up to 100Mbps Uses part of the Telstra 4G Mobile Network Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $23/mth Min. cost $23 Go to Site	$23/mth Min. cost $23	Go to Site
#2	Tangerine Telecom	Tangerine Telecom 25GB 5G Mobile SIM 25GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $29/mth Min. cost $29 Go to Site	$29/mth Min. cost $29	Go to Site
#3	Tangerine Telecom	Tangerine Telecom 32GB 5G Mobile SIM 32GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $34/mth Min. cost $34 Go to Site	$34/mth Min. cost $34	Go to Site
#4	Tangerine Telecom	Tangerine Telecom 50GB 5G Mobile SIM 50GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $40/mth Min. cost $40 Go to Site	$40/mth Min. cost $40	Go to Site
#5	Tangerine Telecom	Tangerine Telecom 80GB 5G Mobile SIM 80GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $46/mth Min. cost $46 Go to Site	$46/mth Min. cost $46	Go to Site
#6	Tangerine Telecom	Tangerine Telecom 150GB 5G Mobile SIM 150GB data at download speeds up to 250Mbps Uses parts of Telstra’s 5G and 4G mobile networks Deal: Bundle your mobile and nbn plans on the same account to get 10% off your mobile SIM-only plan fees. T&Cs apply. $58/mth Min. cost $58 Go to Site	$58/mth Min. cost $58	Go to Site

Roaming in Thailand with Belong

Belong has a fairly short list of countries it offers roaming in and luckily Thailand is one of them. This Telstra MVNO offers one simple add-on that includes 3GB of data, unlimited texts and 150 minutes of calls. It has a 15-day expiry and costs $30.

You can use this roaming add-on on the following Belong plans:

#1	Belong	Belong 25GB Mobile Plan 25GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks $30/mth Min. cost $30 Go to Site	$30/mth Min. cost $30	Go to Site
#2	Belong	Belong 40GB Mobile Plan 40GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks $35/mth Min. cost $35 Go to Site	$35/mth Min. cost $35	Go to Site
#3	Belong	Belong 100GB Mobile Plan 100GB data at download speeds up to 150Mbps Uses parts of Telstra’s 5G and 4G mobile networks $45/mth Min. cost $45 Go to Site	$45/mth Min. cost $45	Go to Site
#4	Belong	Belong 160GB Mobile Plan 160GB data at download speeds up to 250Mbps Uses parts of Telstra’s 5G and 4G mobile networks $55/mth Min. cost $55 Go to Site	$55/mth Min. cost $55	Go to Site

Roaming in Thailand with amaysim

amaysim (an Optus MVNO) has a slightly different approach to international roaming with four different packs with varying inclusions for the person. Each pack has a 365-day expiry meaning there's no need to use it all at once.

Here are amaysim's international roaming packs:

Pack	Price	Inclusions
Small Talk	$20	100 mins, 100 texts, no data
The Works	$25	50 mins, 30 texts, 2GB
Just Gigs	$50	No mins, no texts, 6GB
The Epic	$70	100 mins, 60 texts, 9GB

These roaming packs can be added on the following 28-day expiry prepaid plans:

#1	amaysim	amaysim UNLIMITED 10GB Plan 10GB data at download speeds up to 100Mbps On the Optus 4G Plus Mobile Network $22 Per 28 Day Renewal Link not supplied	$22 Per 28 Day Renewal	Link not supplied
#2	amaysim	amaysim UNLIMITED 32GB Plan 32GB data at download speeds up to 100Mbps Optus 5G in selected areas with 5G devices ex. NT Deal: Save $20 & get 18GB bonus data for first renewal when you sign up by 30.04.25. Online only. T&Cs apply $30 Per 28 Day Renewal Link not supplied	$30 Per 28 Day Renewal	Link not supplied
#3	amaysim	amaysim UNLIMITED 80GB Plan 80GB data at download speeds up to 100Mbps Optus 5G in selected areas with 5G devices ex. NT Deal: Save $25 for first renewal when you sign up by 30.04.25 $40 Per 28 Day Renewal Link not supplied	$40 Per 28 Day Renewal	Link not supplied
#4	amaysim	amaysim UNLIMITED 120GB Plan 120GB data at download speeds up to 150Mbps Optus 5G in selected areas with 5G devices ex. NT $50 Per 28 Day Renewal Link not supplied	$50 Per 28 Day Renewal	Link not supplied

Roaming in Thailand with Telstra

Thailand is designated a Zone 2 country by Telstra which means your option for roaming in Thailand is to grab an International Day Pass. Telstra's Day Pass includes unlimited calls and texts and 1GB of data for $10 per day. This stays active for 31 after purchase.

The International Day Pass can be activated on the following Telstra postpaid plans:

$65 Basic Upfront SIM Plan

50GB data
Telstra 5G Network in selected areas with 5G devices
Deal: Get your first 3 months device protect on Telstra, then $10/mth.

$65/mth

Min. cost $65

Link not supplied

$65/mth

Min. cost $65

Link not supplied

$75 Essential Upfront SIM Plan

180GB data
Telstra 5G Network in selected areas with 5G devices
Deal: Get your first 3 months device protect on Telstra, then $10/mth.

$75/mth

Min. cost $75

Link not supplied

$75/mth

Min. cost $75

Link not supplied

$99 Premium Upfront SIM Plan

300GB data
Telstra 5G Network in selected areas with 5G devices
Deal: Get your first 3 months device protect on Telstra, then $10/mth.

$99/mth

Min. cost $99

Link not supplied

$99/mth

Min. cost $99

Link not supplied

Telstra prepaid customers have the option of purchasing one of the following international roaming packs:

Pack	Price	Inclusions
3-day expiry	$10	15 mins, 15 texts, 400MB
7-day expiry	$15	25 mins, 25 texts, 2GB
14-day expiry	$25	50 mins, 50 texts, 4GB

Roaming in Thailand with Boost Mobile

Thailand is one of the 40 countries where Boost Mobile offers International Roaming Packs.

Boost Mobile customers can choose between three roaming options:

Pack	Price	Inclusions
Three-day expiry	$20	15 mins, 15 texts, 1GB
Seven-day expiry	$30	30 mins, 30 texts, 3GB
14-day expiry	$40	60 mins, 60 texts, 5GB

You can see Boost's prepaid plans with 28-day expiry here:

#1	Boost Mobile	Boost Mobile $26 Prepaid 17GB data at download speeds up to 150Mbps Telstra 5G Network in selected areas with 5G devices Deal: Get 17GB data for the first 3 recharges, then 7GB from 4th recharge. New customers only. Activate by 07.07.25 $26 Per 28 Day Renewal Go to Site	$26 Per 28 Day Renewal	Go to Site
#2	Boost Mobile	Boost Mobile $39 Prepaid 65GB data at download speeds up to 150Mbps Telstra 5G Network in selected areas with 5G devices Deal: Grab a $39 SIM for $13 – save $26. Hurry! Offer ends 12 May 2025. Terms Apply $39 Per 28 Day Renewal Go to Site	$39 Per 28 Day Renewal	Go to Site
#3	Boost Mobile	Boost Mobile $49 Prepaid 95GB data at download speeds up to 150Mbps Telstra 5G Network in selected areas with 5G devices Deal: Get 95GB data for first 3 recharges, then 35GB from 4th recharge. New customers only. Activate by 07.07.25 $49 Per 28 Day Renewal Go to Site	$49 Per 28 Day Renewal	Go to Site
#4	Boost Mobile	Boost Mobile $59 Prepaid 120GB data at download speeds up to 250Mbps Telstra 5G Network in selected areas with 5G devices Deal: Get 120GB data for the first 3 recharges, then 45GB from 4th recharge. New customers only. Activate by 07.07.25 $59 Per 28 Day Renewal Go to Site	$59 Per 28 Day Renewal	Go to Site
#5	Boost Mobile	Boost Mobile $74 Prepaid 160GB Uncapped download speed Telstra 5G Network in selected areas with 5G devices Deal: Get 160GB data for the first 3 recharges, then 90GB from 4th recharge. New customers only. Activate by 07.07.25 $74 Per 28 Day Renewal Go to Site	$74 Per 28 Day Renewal	Go to Site

Use free public WiFi in Thailand

If you're only planning to be in Thailand for a few days then you might not need to worry about a Thailand travel SIM or roaming at all. Free WiFi is available in many public spaces across the country. With the right apps you can call, message and video chat with people back home in Australia.

The downside of using free public WiFi is that it may not be available everywhere and where it is available it may have a time limit.

Hot tip

If you're opting to chase after free WiFi make sure you set your phone to airplane mode when not connected or double and triple check you've turned off data roaming so you don't get hit by fees from your telco.

SIM cards for travelling in Thailand FAQs

Can you buy a Thailand SIM card in Australia?

Yes, if you want to purchase your Thailand SIM card ahead of time you can order it from online stores such as SIMsDirect or SIMCorner who deliver to Australia. SimsDirect offers plans on the DTAC network and SIMCorner's operate on the AIS network.

Remember to double-check what's included in your plan.

Can I use my Australian phone in Thailand?

Yes, so long as your device is unlocked you will be able to use your Australian phone in Thailand.

Is it cheaper to get a SIM card in Thailand?

It all comes down to how long you plan to visit Thailand. It's a better idea to get a cheap Thailand the longer your trip becomes. For example even with Vodafone's $5 a roaming you'd end up spending $70 for a 14-day trip. eSIMs for Thailand (such as Airalo) are particularly cheap for how much data you can get.