Before you start

Your original passport — photos or photocopies are no longer accepted for registration
An unlocked phone (most modern handsets; check eSIM support if going that route)
A Thai address if you want a postpaid (monthly contract) plan rather than prepaid

Step-by-step

1
Decide: tourist pack, prepaid, postpaid, or eSIM
Short stay: a tourist prepaid pack (heaps of data for 7-30 days) is simplest. Staying longer: a standard prepaid SIM you top up, or a postpaid monthly plan if you have an address and want a bigger allowance. Want to skip the registration counter entirely? Buy an eSIM online before you fly.
OnlineWho: YouA few minutes to decideFree to choose
2
Buy from an official store, not a random stall
All three carriers (AIS, True, dtac) have official stores in the arrival halls of Bangkok's airports and in every major mall. Buying from an official AIS/True/dtac shop (or a reputable airport counter) means the SIM is registered correctly the first time and you get help in English.
In personWho: You~15-30 minTourist data packs roughly 200-600 THB; standard SIM from ~50 THB
3
Register the SIM to your passport (biometric check)
Staff scan your passport and, under the NBTC's tightened rules, run a facial-recognition liveness check to confirm you are the holder — similar to a banking-app selfie, takes about a minute. The SIM is then tied to your identity. Note you can hold at most three SIMs per operator.
In personWho: You (with shop staff)~5-10 minIncluded
4
Top up and add a data package
Prepaid credit alone is poor value — always add a data package on top via the carrier app (myAIS, TrueID/iService, dtac), a top-up machine, or any 7-Eleven. Packages are cheap by global standards; unlimited or large-bucket monthly options are easy to find.
Mobile appWho: You~5 min~200-400 THB/month for a generous data package
5
Or activate an eSIM and skip the queue
If your phone supports eSIM, you can buy and install a Thailand data eSIM online (carrier or travel-eSIM provider) and have data the moment you land — data-only eSIMs generally do not require the passport-counter registration that physical SIMs do. The trade-off is you may not get a usable local voice number.
OnlineWho: You~10 min, before or on arrivalData eSIM roughly 250-700 THB depending on data/validity

Documents you’ll need

Original passport (mandatory for physical-SIM registration)
Your phone (unlocked; eSIM-capable if using an eSIM)
Thai address (only for postpaid/monthly contracts)
Cash or card for the SIM and top-up

Things most newcomers don’t know

You must register in person with your real passport — and pass a face scan.

Thailand enforces SIM registration through the NBTC, and the rules have tightened to require original-document checks plus facial-recognition (liveness) verification at the counter. Photocopies and remote sign-ups no longer cut it, so bring your actual passport and expect a quick selfie-style scan.

Source: NBTC / Lex Bangkok 2026

eSIM is the cleanest way around the registration friction.

Data-only travel eSIMs are generally sold online without the passport-counter registration that physical SIMs require, so you can land already connected. The catch is you often get data but not a proper Thai voice number — fine for most newcomers who live on data apps, less so if you need to receive Thai SMS or calls.

Source: Saily / Yozzo eSIM analysis

Buy at an official AIS/True/dtac store, not just any shop.

Official carrier stores in airport arrival halls and malls register the SIM correctly, speak English, and steer you to the right package. Independent stalls can misregister a SIM or oversell weak packages, which is a headache to fix once you have left.

Source: carrier / traveller guides

Always add a data package — raw prepaid credit is a trap.

Pay-as-you-go data billed against plain credit burns money fast. The cheap, generous deals are the add-on data packages bought through the carrier app or at 7-Eleven. A few hundred baht buys a month of comfortable data, so activate a package immediately after registering.

Source: traveller-guide consensus

Common mistakes to avoid

Bringing only a photocopy or photo of your passport — registration now needs the original
Expecting to register remotely; physical SIMs require an in-person identity (and face) check
Buying a SIM from an unofficial stall and getting it misregistered or oversold
Running on plain prepaid credit instead of adding a cheap data package
Assuming a data-only eSIM gives you a usable Thai voice/SMS number