Free eSIM for Thailand: 1 GB, and the Arrival Card Nobody Mentions

Thailand now asks every foreign visitor to fill in an online arrival card before they land, which makes turning up without data a worse idea than it used to be. co:sim's free new-user eSIM for Thailand is 1 GB valid for 7 days, $0 at checkout, installed before you fly and live the moment you touch down at Suvarnabhumi, Don Mueang, Phuket or Chiang Mai.

This guide covers the arrival-card requirement, which Thai networks carry the eSIM, whether 1 GB survives a week, and how the free trial fits alongside the ฿299 airport SIMs everyone recommends.

#Do you need mobile data to enter Thailand now?

Not strictly at the border, but the process assumes you have it. Since 1 May 2025 every non-Thai national entering Thailand by air, land or sea must submit the Thailand Digital Arrival Card, and the official portal at tdac.immigration.go.th is the only place to do it — Thai Immigration stresses that it is free and warns against third-party sites charging for it.

The submission window is narrow. You may only file it in the three days before arrival, so it is not something you complete months ahead with the rest of your booking. That means one online task landing squarely in the window where many travellers are already in transit.

Immigration's own TDAC FAQ confirms kiosks and Wi-Fi are provided on arrival for anyone without a connection, so nobody is turned away for lacking a phone. But filling the form in an arrivals queue on borrowed Wi-Fi is a worse experience than doing it from your hotel the night before, and a connection you already own removes the question entirely.

#Which Thai networks will carry it?

co:sim's Thailand plans roam onto AIS, TrueMove H and DTAC, all with 5G. The plan page names the underlying network before you buy, which matters here because the three networks are not interchangeable outside Bangkok.

Thailand's mobile coverage is among the strongest in Southeast Asia. Opensignal's August 2026 Thailand report found TrueMove H winning 5G Availability outright at 90.2%, meaning users with a 5G handset detect a 5G signal the overwhelming majority of the time, while AIS defended the Upload Speed award at 15 Mbps — around a third faster than second place.

That 90.2% is a signal-detection figure for populated areas, not a promise about the whole country. In practice: excellent in Bangkok, Chiang Mai, Phuket and the main island towns; thinner on the roads up to Doi Suthep and out towards Mae Hong Son; and gone in the middle of the Surat Thani to Samui crossing. Download offline maps for island-hopping days.

#Is 1 GB enough for a week in Thailand?

For maps, messaging, Grab and the arrival card, comfortably. For video, no. A day of navigating Bangkok with a routing app open on and off, plus messaging and a few Grab bookings, lands somewhere around 80–150 MB. Seven days of that fits inside 1 GB with room to spare.

What empties it is media. A single 10-minute clip at 1080p is roughly 300 MB, a third of the allowance in one sitting, and photo backup on a beach holiday will finish the job faster. Turn off automatic photo upload on cellular before you land; it is the one setting that decides whether the trial lasts the week.

These plans are reloadable, so if you do run out you top up from the co:sim account dashboard and the same eSIM profile keeps working, with no reinstall and no second QR code.

FREEClaim the free eSIM for Thailand

#Why not just buy a ฿299 SIM at the airport?

For a two-week trip you probably should, and the AIS and TrueMove H counters at Suvarnabhumi are impossible to miss. Tourist SIMs there run roughly ฿299–599 for 15–50 GB, many times what the free trial gives you. If you intend to stream, tether a laptop or work remotely, that is the correct purchase and this article is not arguing otherwise.

The free eSIM is aimed at a different part of the trip. Thai regulations require prepaid registration, so the counter scans your passport and links it to the SIM before it activates — a queue and a document check standing between a 06:00 arrival and your first Grab booking.

There is also the geometry of Suvarnabhumi itself. Grab pickup is on a specific floor, the app tells you which one, and the Airport Rail Link to Phaya Thai runs about 26 minutes for ฿45 with a BTS connection at the other end. Those are decisions you make better with a working phone than with a paper map and a taxi tout.

#How do you claim and install it before you fly?

Install at home on Wi-Fi, activate on arrival. Installing an eSIM needs an internet connection, so doing it at the airport in Thailand is the same chicken-and-egg problem it is everywhere else.

1. Open the free eSIM page for Thailand and claim it. One per new customer, $0 at checkout.
2. co:sim emails the QR code within seconds of checkout.
3. Scan it on home Wi-Fi. iPhone: Settings → Cellular → Add eSIM. Most Android: Settings → Network & internet → SIMs → Add eSIM.
4. File your TDAC in the three days before departure, from a connection you trust.
5. On landing, switch the co:sim line on and enable data roaming for that line only.

Each co:sim plan page states its install deadline, so you can see how far ahead of a trip it is safe to buy rather than guessing at it.

Continuing to Singapore, Kuala Lumpur or Bali on the same trip? These are separate cards with no roaming between them, so a Southeast Asia regional plan is the sane option for an overland loop.

#FAQ

#Is the free eSIM for Thailand the same offer as co:sim's free eSIM for Europe?

No. co:sim's new-user free eSIM is a single promotion funded across several genuinely different products, and the cards are not interchangeable. One is a regional plan covering 33 European countries on one profile. The Thailand version is its own single-territory plan: it works throughout Thailand and stops at every border, including the crossings into Malaysia, Cambodia and Laos. Turkey, Moldova, Singapore, Malaysia, Indonesia, Japan and South Korea each have their own separate card on the same basis. The promotion can be claimed once per new customer, so this is a decision about which country to take it for, not a set to collect. If you are doing an overland Southeast Asia loop, claim it for wherever you fly into and buy a paid regional plan for the rest.

#Does it work on the islands and on the ferries?

On the islands, yes. Phuket, Samui, Phi Phi, Koh Tao and Koh Chang all have solid coverage in their populated areas, which is where accommodation, restaurants and pier offices actually are. On the water it depends entirely on distance from shore: the long-tail boat between Krabi and Railay stays inside coverage the whole way, while the middle of the Surat Thani to Samui crossing and the run out to the Similans drop to nothing at all. Because a co:sim eSIM roams onto the same Thai national networks local subscribers use rather than some separate tourist network, you get what a Thai phone gets in the same seat. Download offline maps and your ferry ticket before boarding, and expect the signal to return as the next island comes into view.

#Do I still need to fill in the Thailand Digital Arrival Card?

Yes. Since 1 May 2025 the TDAC is mandatory for all non-Thai nationals arriving by air, land or sea, regardless of visa type, and it is separate from any visa you may hold. You submit it online no more than three days before arrival, and only through the official Thai Immigration portal, which is free — sites charging a fee for it are not official. Immigration provides kiosks and Wi-Fi on arrival for travellers with no connection, so having an eSIM is not a legal requirement. It is a practical one: filing the form calmly the night before, from a connection you control, beats doing it standing in a queue on a network you are sharing with a full A380.

#What happens when the 1 GB or the 7 days run out?

Whichever limit you reach first ends the plan's data. The seven days start at first connection rather than at purchase, so installing the profile a week or two before your flight does not silently consume the validity — the clock starts when the eSIM first attaches to a Thai network. Once the allowance is gone, these plans are reloadable: you top up from the co:sim dashboard and the same profile keeps working, with no reinstall and no new QR code. You can also switch to a paid Thailand plan with a bigger allowance, or buy a counter SIM if you happen to be near an airport. Nothing on the phone breaks when the free plan ends; the line simply stops carrying data until you top it up.

#Does it work on the BTS and MRT, and can I use a hotspot?

Both, yes. The elevated BTS has continuous coverage along its length, and the underground MRT carries mobile signal through the tunnels, so a map keeps updating between stations instead of freezing when you go below ground. That matters in Bangkok, where the fastest route across the city at six in the evening is almost always the one that avoids the road. Hotspot is enabled, and sharing with a travelling companion is the normal way people use a small allowance. The arithmetic is the constraint rather than any rule: a tethered laptop draws from the same 1 GB and cloud sync will empty it quickly. For deliberate sharing across a whole trip, a paid Thailand plan with a larger allowance is the better buy, with the free trial covering the airport.

Ready to arrive with the arrival card already filed and a working map? Claim the free eSIM, install it tonight, and switch it on when you land.

Browse co:sim's Thailand eSIM plans