Best eSIM for Thailand: Network, Price and the Daily Data Cap Compared

Which eSIM Is Best for Thailand?

Thailand is one of the easiest countries in Southeast Asia to stay connected in, right up until your trip leaves Bangkok's main roads for a boat between islands or a mountain pass on the Mae Hong Son loop. Most "best eSIM for Thailand" lists are really written for that first part of the country, not the whole thing. Two networks actually run Thailand: AIS on one side, and the merged True and dtac network on the other, and which one your eSIM connects to changes depending on where your itinerary goes. Roamic's Thailand eSIM is a genuinely strong option for most trips here, and so are Airalo, Saily, and Holafly, but none of them handle network, price, or data caps quite the same way, and that's what this guide actually compares. (If you haven't confirmed your phone even supports eSIM, check that before reading any further, it's a two-second look in your settings.)

Which Network Does Your eSIM Actually Use?

Most Thailand eSIM content treats "network" as a footnote. It shouldn't be. AIS and True/dtac are genuinely separate pieces of infrastructure with their own towers, their own coverage gaps, and their own strengths, and a provider that never says which one you're getting is quietly deciding that for you.

Which Provider Runs on Which Network

Provider	Network(s)	Disclosed?
Roamic	TrueMove H, dtac	Yes, stated on the Thailand eSIM product page
Airalo	Varies by plan, some run AIS plus True, others are dtac-branded	Yes, but changes by which specific plan you pick
Saily	Not disclosed	No
Holafly	True / dtac	Yes

Here's the one honest limitation worth stating plainly: Roamic's Thailand eSIM doesn't run on AIS. For a trip that stays in Bangkok, Chiang Mai's old city, or Phuket's main beaches, that's close to irrelevant. Once your itinerary heads for the Gulf islands or the mountains north of Chiang Mai, it starts to matter, and the next two sections say exactly where.

Coverage on Koh Samui, Koh Tao and Koh Phi Phi

The developed parts of all three islands are fine on any network. Chaweng and Lamai on Samui, the main pier and dive shops on Koh Tao, and Tonsai village on Phi Phi all carry a strong signal regardless of carrier. Push past that, though, and AIS pulls ahead. Multiple independent travelers report the same pattern on Samui and Koh Phangan: AIS holds a signal on the ring road and through ferry crossings where True/dtac starts to fade. Koh Tao's east-side dive sites and viewpoints thin out for both networks, and the isolated bays on Phi Phi, reachable only by boat, drop off entirely no matter what's in your phone.

Where the Signal Drops: Khao Sok, Mae Hong Son, the Bangkok to Chiang Mai Train

Three specific spots worth knowing before you're standing in them with no bars.

Khao Sok National Park has coverage at the entrance and around the floating bungalows on Cheow Lan Lake, and nothing once you're deep in the jungle trails or out on the lake itself. Treat any overnight stay there as a scheduled break from your phone, not a connectivity problem to solve.

The Mae Hong Son loop, the mountain route northwest of Chiang Mai, is the clearest case where network choice actually shows up in real life. AIS has a consistent, well-documented edge on the winding passes here. True and dtac users report solid coverage in the towns along the loop and patchy-to-nothing on the roads between them.

The overnight train between Bangkok and Chiang Mai doesn't reliably have wifi. Some of the newer trainsets do, plenty of the older ones don't, and you won't know which you've got until you board. Mobile signal holds up fine across the central plains and drops through the mountainous stretch near the historic Khun Tan Tunnel, the highest point on the line. Download whatever you need before the train leaves the station, not somewhere in the hills north of Lampang.

Do You Have to Register a SIM Card in Thailand?

Sort of, and the distinction matters. Thai law requires passport registration, and since 2025 a biometric liveness check, for a physical Thai SIM or a Thai carrier's own eSIM bought directly from AIS, True, or dtac, whether that's at a mall shop or an airport kiosk. That's a real step, not a formality, and it takes a few minutes even when the staff handle most of it.

An international travel eSIM, Roamic included, skips this for you. You're not becoming an individual subscriber with a Thai carrier. The provider handles that relationship on its own bulk arrangement, and your passport never enters the transaction. If avoiding a registration line is part of why you're reading this, it's a genuine reason to buy before you fly rather than after you land.

What "Unlimited" Means in Thailand: the Daily Throttle

"Unlimited" on a Thailand eSIM almost never means what it sounds like. It means a fixed amount of full-speed data every 24 hours, after which your connection keeps working but slows down considerably until the cycle resets. That's not a hidden catch so much as an industry-wide structure, but how openly each provider states the number is where they start to differ. Roamic and Airalo both disclose theirs outright: 3GB a day at full speed, then throttled to roughly 1Mbps until the next 24-hour cycle resets. That's still enough for maps, messaging, and most browsing, just not smooth video streaming. Holafly and Saily don't publish a number for Thailand at all, which means you're buying a promise you can't actually check.

How Many Days Do You Need: 7, 15 or 30?

This is really a matching question, not a fixed menu. Roamic's Thailand eSIM lets you set your own day count and data amount, or switch to the Unlimited plan entirely, and the price adjusts automatically based on what you pick. That flexibility is the point of this section: instead of forcing your trip into someone else's three preset tiers, you're matching the plan to the days and data your specific route actually needs.

Matching Plan Length to an Island-Hopping Route

Here's how a common Gulf-islands route breaks down, leg by leg:

• Bangkok (2 to 3 nights): heaviest data days, maps, Grab, hotel and ferry bookings.
• Ferry to Koh Samui (travel day): expect a signal-free stretch once you clear the harbor.
• Koh Samui (3 to 4 nights): strong coverage in Chaweng and Lamai, patchier on the ring road's quieter stretches.
• Ferry to Koh Tao (travel day): another dead crossing, download your next stop's offline map before boarding.
• Koh Tao (3 to 4 nights): solid near the pier and dive shops, thinner at the east-side viewpoints.
• On to Koh Phi Phi (2 to 3 nights): good signal in Tonsai village, little to none on boat-access-only bays.

That's realistically 12 to 15 days once the crossings themselves are counted, which puts most of this route in Roamic's 10GB/30-day or 20GB/30-day range rather than the shorter tiers.

Trip type	Roamic plan that fits	Why
Long weekend, Bangkok only	1GB / 7 days (€0.99)	Light maps-and-messages usage over a short stay
One island, a week or so	3GB / 14 days (€2.99) or 5GB / 21 days (€4.99)	Covers a single base with day trips, without paying for days you won't use
The island-hopping route above (12 to 15 days)	10GB / 30 days (€8.99)	The 30-day window covers the full route even if it runs long, with data to spare for photos and video calls home
Heavier daily use, streaming, video calls, content creation	Unlimited plan	Set-and-forget instead of tracking a gigabyte count against a moving itinerary

The 20GB and 50GB/30-day tiers exist for longer stays or multiple travelers sharing data needs, but for the route above, 10GB/30 days is the one that actually matches what you'd use.

Where to Buy an eSIM for Thailand (and Where Not To)

Before You Fly vs. at Suvarnabhumi Airport

Buying before you fly means you land already connected, no queue, no passport handover, and no dependence on which counter happens to be staffed when your flight gets in. Installing it is a five-minute process before you ever board, and the full installation steps are laid out separately if you haven't done it before. Suvarnabhumi's arrival hall does have AIS, True, and dtac kiosks, and they're easy enough to find, but they exist to sell you their own registered product, not to save you time.

Why the Airport Counter Is Not Cheaper

On paper, airport SIM prices aren't wildly different from what you'd pay at a mall shop in the city, typically somewhere between 300 and 1,200 baht depending on data and validity. The real cost is what happens at the counter. There's a documented pattern of kiosk staff steering tired, jet-lagged tourists toward the priciest tourist plan on the rack rather than mentioning the cheaper one two feet away, plus the registration itself, plus however long the queue runs on a busy arrival bank. None of that shows up in the sticker price, and all of it disappears if you've already installed something before you left home.

What Does an eSIM for Thailand Cost?

Price Comparison: Roamic, Airalo, Saily, Holafly

The cheapest way into each provider, whatever size that happens to be:

Provider	Smallest plan	Price
Roamic	1GB / 7 days	€0.99
Airalo	3GB / 7 days	€5.50
Saily	1GB / 7 days	€2.49
Holafly	Unlimited / 7 days	€25.50

Roamic comes in cheapest at the entry point by a wide margin. Airalo's smallest plan starts at 3GB rather than 1GB, so its higher price reflects more data, not a worse deal outright. Holafly isn't really comparable here since it only sells unlimited time, not fixed data, which is why its 7-day price looks so much higher, you're paying for the cap not existing rather than for a specific amount of data.

Conclusion: Which eSIM for Which Kind of Trip

A Bangkok-and-beaches trip, or really any itinerary that sticks to the country's main tourist corridor, works well on any of the four providers here, and price and plan flexibility end up mattering more than network. Roamic's Thailand eSIM, with its clear per-GB pricing and stated 3GB/day throttle, is a straightforward pick for exactly that kind of trip, and the six-month refund window means a change of dates costs you nothing. Where it's worth pausing is a trip built heavily around the Gulf islands, the Mae Hong Son loop, or long stretches in the northern mountains, where AIS's documented edge is real enough to weigh against everything else on this page. Read the network row, not just the price row, and pick the plan that matches the trip you're actually taking.

Frequently Asked Questions

How Do I Buy an eSIM for Thailand?

Pick a provider, choose your data and day count, and pay online. You'll get a QR code by email that installs in a few minutes over wifi, before you ever leave for the airport.

Where Can I Get an eSIM in Thailand?

Anywhere with an internet connection, technically, but the whole advantage disappears if you wait until you land. Buy and install before you fly so you're connected the moment your plane touches down, not queuing at an arrival-hall kiosk.

What Is the Best eSIM for Thailand?

It depends on your route more than any single "best" pick. For a trip centered on Bangkok, Phuket, or Chiang Mai's main areas, Roamic's clear pricing and disclosed 3GB/day throttle make it a solid, low-friction choice. For a trip built heavily around the Gulf islands or the northern mountain loops, weigh that against AIS's documented coverage edge before deciding.

Do I Need to Register a SIM Card in Thailand?

Only for a physical Thai SIM or a Thai carrier's own eSIM, and yes, that means a passport and a biometric check as of 2025. An international travel eSIM bought before you fly skips this step entirely for you.