The quickest way online in Thailand is a tourist SIM bought on arrival: coverage is strong in every city and on the main islands, prices are low, and the two national networks sell purpose-made tourist packages at the airport. The catch is a passport-registration rule that applies to every SIM, tourist or not.
Buying a tourist SIM
Thailand’s two networks are AIS and True-dtac, the merged entity formed when True and dtac combined their mobile business. True-dtac’s Tourist Infinite SIM comes in four validities, each with unlimited data and free local calls to all Thai networks up to 15 minutes per call, with out-of-bundle rates applying beyond that: 5 days for THB 349, 8 days for THB 449, 15 days for THB 699 and 30 days for THB 1,199. Unlimited data plans like these carry a daily fair-use cap before speeds are throttled, so read the small print if you plan to tether a laptop all day. AIS sells an equivalent range under its own tourist-SIM branding at airports and convenience stores; compare both counters before you buy, since promotions change more often than this page does.
Both operators sell physical SIMs and eSIMs at Suvarnabhumi and Don Mueang arrivals, at AIS and True shops, and at 7-Eleven and other convenience stores nationwide. An eSIM saves you queuing at the airport if your phone supports one and you can install it before you fly, using the free arrival Wi-Fi to finish activation.
The registration rule
Every SIM sold in Thailand, prepaid or postpaid, must be registered against a photo ID before it works. For a tourist buying at an airport counter or convenience store this means handing over your passport; the shop scans it and activates the SIM on the spot, a process that takes a few minutes. Rules tightened under a 2025 National Broadcasting and Telecommunications Commission order: foreign nationals can register no more than three SIMs per operator, and a tourist SIM’s validity is capped at 60 days with no option to extend it by topping up — once it expires you register a new one rather than renewing the old.
Roaming from home
Thailand is not part of any roam-like-at-home bloc, so EU, UK and US travellers pay whatever their own operator charges for roaming there, and that is almost always more expensive per gigabyte than a local SIM. If you only need occasional maps and messaging for a short trip, a roaming day-pass from your home operator can still beat the hassle of swapping SIMs; check the price per day against the tourist SIM prices above before deciding.
Wi-Fi
Hotels, cafés and malls in tourist areas almost all offer free Wi-Fi, so a SIM matters most for the time between them. At Suvarnabhumi Airport, the network “AOT Airport Free Wi-Fi by NT” gives you 60 minutes of free access per connection, enough to look up a taxi counter or confirm a hotel booking while you set up a local SIM.
Power and calling
Thailand uses the plug types and calling code shown in the facts box on this page; pack an adapter that matches, and drop the leading zero from a Thai number when dialling in from abroad.
Practical tips
- Bring your passport to the SIM counter, not a photo of it; some shops insist on the physical document.
- An eSIM avoids losing a physical card if you switch phones or SIMs partway through a trip, but confirm your model is unlocked and eSIM-compatible before you leave home.
- Unlimited tourist plans throttle after a daily data cap rather than stopping outright, so heavy video calls or backups are still possible, just slower.
- Keep your home SIM active (or use a dual-SIM/eSIM phone) so you can still receive bank verification texts while the Thai SIM handles data.
What to check before you go
- Whether your phone is unlocked and supports eSIM, so you can compare physical and eSIM tourist plans.
- The current True-dtac and AIS tourist SIM prices at the airport, since promotions shift often.
- Your home operator’s Thailand roaming rate, in case a short trip is cheaper on a day-pass than a new SIM.
- That you are carrying your passport for SIM registration, and that a tourist SIM’s 60-day cap fits your length of stay.