Thailand SIM Card

The two cost exactly the same, so pick by where you're going. AIS has the widest coverage, and in Opensignal's August 2026 report it won coverage, 5G coverage and consistent quality, the measures that matter on a ferry, in a national park or in a village in Isan. For a trip with islands, Khao Sok or the mountains in the north, I'd take AIS.

True merged with dtac in 2023 and they now share one network, which had the fastest downloads in the same report (dtac's 41 Mbps average was the best in the country) and the widest 5G availability. If you're mostly in Bangkok, Chiang Mai and Phuket, True is as good or better, and its 8-day and longer SIMs include unlimited calls to Thai numbers, which is handy for calling hotels, drivers and dive shops. True's ฿349 10-day SIM is the cheapest unlimited data you can buy, but it can't make calls or send texts.

The airport is the easiest place, because the staff register the SIM to your passport, put it in your phone and check it works before you leave. At Suvarnabhumi, True has shops on the 2nd floor arrivals level by Gates 4, 5, 6 and 10, and AIS has counters in the same hall. At Don Mueang the counters are at international arrivals exits 3, 4 and 6, at Phuket in Terminal 2 next to Exit 3, and at Chiang Mai near Exit 10. True says its airport counters are open 24 hours.

In town, AIS and True shops sell the same tourist packages, and most big malls have one. 7-Eleven sells top-up credit for both networks, but the tourist SIMs themselves are an operator-shop product, so buy at the airport or a mall shop rather than counting on the corner store.

You can also book True's tourist SIM on Klook and pick it up at Klook's counter on the 2nd floor at Gate 1 of Suvarnabhumi, which suits a midnight arrival when you'd rather not queue. Those pickup SIMs have outgoing calls and texts switched off until you verify your identity at a True Shop, so treat them as data SIMs.

Thailand tightened SIM registration in 2025 to fight phone scams. Every SIM has to be registered to the holder's passport, a foreigner can hold up to three numbers per operator, and since a Royal Gazette notice in August 2025 a tourist SIM lasts 60 days at most and can't be extended with top-ups. The counter staff do the registration for you; buying online usually means verifying your identity in an app or at a shop before calls work.

Staying longer than 60 days means re-verifying the number. On AIS you text your passport number to 4444161 and follow the link, or visit an AIS shop. With the visa-free stay now 30 days, the 30-day package covers most trips, and anyone on a longer visa is better off with a regular prepaid SIM from an operator shop.

The unlimited packages don't run out of data, so most visitors never top up. Credit for calls beyond the included minutes is sold at 7-Eleven and the operators' shops, in ฿20, ฿50, ฿100 and ฿300 amounts for True, and through the myAIS app or AIS's website for AIS. On True, *123# shows your balance, and *900*1756# adds 3GB for 8 days for ฿150 if you've chosen a capped plan.

Tourist SIMs can't be extended past 60 days, so buy the length you need at the start.

Roaming is the expensive option. T-Mobile's international pass is $10 a day for 2GB, or $50 for 10 days; AT&T and Verizon charge $12 a day; EE charges £6 a day or £50 for 15 days, and Three £7 to £8. Eight days on any of them costs more than a month on a Thai SIM.

A travel eSIM is the alternative to the counter. You install it at home, it runs on the same AIS and True networks, and you land with data, while your home SIM stays in the phone for bank codes. For a week or two with moderate use it's cheaper than a tourist SIM. The tourist SIM wins for heavy data and long trips, and it's the only option with a Thai phone number, which Grab drivers, hotels and restaurants will call. If your phone is older than about 2018 it may not take an eSIM, and then the SIM decides itself.