SIM cards & mobile data in Thailand: AIS, True, eSIM & the registration rule

Why your SIM is a relocation task, not a souvenir

In Thailand your mobile number quietly becomes the key to daily life: it receives the one-time password (OTP) that logs you into your Thai bank, it’s tied to your Grab, food-delivery and ride apps, and it’s the contact number on lease, immigration and utility paperwork. Getting the right SIM early — and not losing the number later — saves real friction. This guide is the operational companion to our broader internet & mobile guide: that one covers staying connected end-to-end including home fibre and the bank-OTP trap; this one drills into the SIM and data mechanics themselves — networks, registration, prices, eSIM and topping up. None of this is legal advice; operator plans and rules change, so verify current details on the network’s own app or site.

The networks: AIS, True (and dtac), NT

Thailand effectively runs on a small number of national operators, and after consolidation the choice is simpler than it looks:

• AIS — the market leader, with the widest and most consistent nationwide coverage, including remote provinces and islands. The safe default if you travel around Thailand or want the fewest dead spots.
• True — after True and dtac merged in 2023 under True Corporation, this is now a single very large network. Coverage in Bangkok, major cities and tourist areas is excellent and plans are often a touch cheaper; the dtac brand SIMs you’ll still see run on the combined network.
• NT (National Telecom) — the smaller state operator. It exists and can be cheap, but coverage and English support make it a rare pick for newcomers.

For day-to-day data, both AIS and True deliver fast 4G nationwide and 5G across the cities. If you’ll spend most of your time in Bangkok, Chiang Mai, Phuket or Pattaya, either is excellent; if you head into rural areas often, lean AIS.

Tourist SIM vs local prepaid vs postpaid

There are three tiers, and picking the wrong one is the most common newcomer mistake:

A clean path is: tourist SIM on arrival → convert/replace with local prepaid once you have your phone and a few days’ orientation → consider postpaid later if you want a bigger plan. Whatever you choose, the number you register first is the one to keep and protect (see porting, section 09).

The registration rule: passport and biometrics

This is non-negotiable and catches some people out. SIM registration has been mandatory in Thailand since 2015, so you must present your passport to activate any SIM — tourist or local. With biometric registration now standard at official outlets, buying in an operator shop or airport counter frequently also involves a quick face scan or photo tying the SIM to you.

• Buy from an official AIS/True shop or airport counter so the registration is done correctly in your name — not from an informal reseller.
• Keep the phone number and the receipt; the number is what your bank, ride and delivery apps will be locked to.
• An unregistered SIM is generally not legal to use and can be cut off — always complete registration at purchase.

What data actually costs

Mobile data is genuinely cheap here. Treat these as indicative ranges — promotions change constantly, so confirm the current bundle in the operator’s app:

• Tourist SIMs: roughly 300–900 baht for 8–30 days, typically with generous or “unlimited” data plus some call credit.
• Ongoing prepaid data packages: roughly 200–600 baht a month for a solid allowance — often tiered as a chunk of high-speed data then unlimited at a capped speed.
• Unlimited high-speed: available at a higher monthly price for heavy users and remote workers who tether.
• Pay-as-you-go data without a package is expensive per megabyte — always add a package right after activating the SIM.

Where you live shapes whether mobile data alone is enough: a city condo with cheap home fibre means your SIM just covers you out and about, while a remote stay may lean harder on mobile data — see the internet & mobile overview for the home-broadband side.

eSIM and data-only options

If your phone supports it, eSIM removes the physical-card swap entirely:

• Local eSIM (AIS / True): both support eSIM on compatible handsets — activate via the app or in-shop with your passport (registration rules still apply). Best long-term option because you get a Thai number for OTPs and apps.
• International travel eSIM: global providers run on Thai networks and install before you arrive, so you land already online. Handy for the first days, but usually data-only (no Thai number), so treat it as a stopgap.
• Data-only SIM / pocket Wi-Fi: useful for tablets, a second device, or a group sharing one connection — a data SIM or rentable pocket Wi-Fi router covers it without touching your main number.

Where to buy

SIMs are sold almost everywhere — the question is doing it once, correctly:

• Airport arrivals hall: official AIS, True and dtac counters sell tourist and local SIMs and set them up on the spot with your passport — the easiest day-one option.
• Operator shops in malls: full-service AIS/True stores in every major shopping centre handle local SIMs, eSIM, postpaid and number porting, usually with English-speaking staff.
• 7-Eleven & Family Mart: thousands of branches sell SIMs and especially top-ups — convenient, though for first-time registration an operator shop is cleaner.

Topping up and managing data

Once your SIM is live, keeping it topped up is simple:

• Add credit via the operator app (myAIS, the True app), mobile/internet banking, an ATM, or by giving your number at any 7-Eleven counter.
• Convert credit into a data package through the app or a short USSD code — the app is by far the easiest way to see your balance and renew.
• Set the package to auto-renew if you can, so a linked number never lapses — an expired prepaid SIM tied to your bank OTP is a headache to recover.

Keeping your number when you switch (porting)

Thailand supports mobile number portability (MNP), so you can move between AIS, True/dtac and NT while keeping the same digits. Request the port at a shop of the network you want to join, show your passport, pay a small fee, and the number transfers within a day or two. This matters because your number becomes tied to bank logins, ride and delivery apps and official accounts — losing it is a real hassle. So chase a better deal by porting, not by starting over, and never let a number-linked SIM expire from inactivity. The same “don’t lose your number” logic underpins the bank-OTP section of our internet & mobile guide.

Where this fits in settling in

A SIM is one of the very first errands of a move, alongside a Thai bank account (which needs your new number for OTPs), sorting utilities, and the first 30 days checklist. Budget-wise, mobile data is a small line — our cost of living guide places it alongside rent, transport and food across realistic lifestyle tiers. Get connected on day one and the rest of the setup goes faster.

Frequently asked