I want the phone working before the bags do. Koh Samui Airport is a small open-air terminal, and it is also the moment Grab, the hotel pin and the transfer driver all want a data connection. If your home plan already roams in Thailand at a price you can stand, use that and stop here. If it does not, install a Thailand eSIM on Wi-Fi at home and switch it on when you land.
For a normal week I would buy Airalo. The 5 GB plan is US$7 for 7 days, it runs on True and AIS, and the operator line says the cover includes Koh Samui. If you barely open anything except maps, Saily’s 1 GB for 7 days is US$2.99, the cheapest plan I could read on a provider’s own page. Yesim is the 30-day shelf. Their checkout would not load past a bot check on 27 Oct 2026, so the Yesim prices below are the indexed storefront that day, which matches the Yesim blog updated 20 Oct 2026.
These three buttons are affiliate links. If you buy through them I may earn a commission, and it does not change the order above. The local SIM is not an affiliate.
Airalo, the one that names Koh Samui
Airalo’s Thailand eSIM is a 5G data-only plan on True and AIS. The operator note I read says it covers the mainland and the islands, and it lists Koh Samui by name, along with Phuket, Krabi and Phi Phi. That is the sentence the other two pages did not give me. The package starts on first use, you have 365 days to start it, and it is rechargeable online. No passport step showed in those operator details.
Fixed plans on the Thailand page, 27 Oct 2026:
| Data | Validity | Price | Per GB |
|---|---|---|---|
| 1 GB | 3 days | US$4.00 | US$4.00 |
| 3 GB | 3 days | US$5.50 | US$1.83 |
| 3 GB | 7 days | US$6.00 | US$2.00 |
| 5 GB | 7 days | US$7.00 | US$1.40 |
| 10 GB | 7 days | US$10.00 | US$1.00 |
| 5 GB | 15 days | US$7.50 | US$1.50 |
| 10 GB | 15 days | US$10.50 | US$1.05 |
| 20 GB | 15 days | US$17.50 | US$0.88 |
| 5 GB | 30 days | US$8.00 | US$1.60 |
| 10 GB | 30 days | US$11.00 | US$1.10 |
| 20 GB | 30 days | US$18.00 | US$0.90 |
| 50 GB | 30 days | US$27.50 | US$0.55 |
Unlimited plans on the same page drop to 1 Mbps after 5 GB in a day: 3 days US$9.50, 5 days US$15, 7 days US$21, 10 days US$31, 15 days US$39, 30 days US$49. I would not buy “unlimited” for a week of maps and Grab. US$21 for 7 days is three times the 5 GB plan, and the speed falls off after 5 GB anyway.
Hotspot is not stated on the package. The help text only says that using a hotspot burns data faster, and that you can top up. Treat hotspot as unconfirmed. Top-up is in the Airalo app when a top-up package exists for that eSIM.
Saily, the cheap short plan
Saily’s own Thailand page, read 27 Oct 2026, says plans start at US$2.99. The cheapest is US$2.99 for 1 GB over 7 days. The cheapest 30-day plan is US$5.99 for 3 GB, which is about US$2.00 per GB. An unlimited 15-day plan was on the page at US$38.99, with 5 GB a day at full speed and then unlimited data at up to 1 Mbps.
Hotspot is “unlimited access with no restrictions”, their words. Top-up is in the app, and the new data starts when the first plan runs out. Buy on the site and you get a QR code by email. Buy in the app and it sits on your profile. Turn the line on and enable data roaming, and Saily says the plan activates when you reach Thailand. The page also says plans have a 180-day window before they activate themselves.
Saily describes coverage “across Thailand” and names Bangkok, Phuket, Chiang Mai and Pattaya. It does not name Koh Samui. I am not going to invent a dead zone, and I am not going to pretend they promised the island. The network name is not on the page either. If the only thing you need is a week of light use and a hotspot for a laptop, this is the plan I would buy. If you want the coverage line that says Koh Samui, that is Airalo.
Yesim, the 30-day shelf
Yesim’s Thailand page sat behind a bot check when I tried to open it on 27 Oct 2026, so I am not going to describe a checkout I did not see. What I could read, from the indexed storefront that day and from the Yesim blog updated 20 Oct 2026, is a set of 30-day prepaid plans:
| Data | Validity | Price | Per GB |
|---|---|---|---|
| 1 GB | 30 days | US$3.12 | US$3.12 |
| 5 GB | 30 days | US$8.40 | US$1.68 |
| 10 GB | 30 days | US$13.20 | US$1.32 |
| 20 GB | 30 days | US$20.40 | US$1.02 |
| 30 GB | 30 days | US$27.60 | US$0.92 |
The 30 GB row is the blog of 20 Oct 2026. The 1 GB, 5 GB, 10 GB and 20 GB rows were also on the indexed storefront on 27 Oct 2026. Hotspot and top-up were not in either of those sources, so both cells stay blank on purpose. You buy it in the Yesim app.
On a pure 30-day data sum, Airalo is cheaper where the plans overlap: 10 GB is US$11 at Airalo and US$13.20 at Yesim, and 20 GB is US$18 against US$20.40. Yesim’s reason to exist on this page is the 30 GB plan, and the fact you should confirm the live price in the app before you pay. I will not dress that up.
A local SIM, if you would rather not use these links
AIS and True sell tourist SIMs in Thailand. A physical SIM has to be registered to a passport. That is the annoying part, and it is also why an eSIM installed at home is what I would do on a short trip. The AIS tourist page was down for maintenance on 27 Oct 2026, so I am not printing a baht price or a day count I could not read. Ask in the shop. This is not an affiliate, and it is the right option if your phone has no eSIM, or if you want a Thai number for a call that WhatsApp will not cover.
Chaweng is where you will actually spend the data: Grab, a menu, a pin for the villa. The photo is the beach road. It is not a shop counter.
Which one should you buy?
| Trip | What I would buy |
|---|---|
| A week, maps, Grab, photos | Airalo 5 GB / 7 days, US$7. 10 GB is US$10 if you post a lot |
| A few days, almost no photos | Saily 1 GB / 7 days, US$2.99 |
| A month, light use | Saily 3 GB / 30 days, US$5.99 |
| A month, heavy use | Airalo 10 GB / 30 days at US$11, or 20 GB at US$18. Open Yesim if you want 30 GB and the app price still matches this table |
| Phone with no eSIM, or you want a Thai number | Local AIS or True SIM, passport, shop price |
Install on Wi-Fi at home. Leave the travel line off until you are in Thailand, or Airalo’s first-use clock starts at the wrong time. Then the ride. The airport transfer guide is the official taxi, Welcome Pickups, Kiwitaxi and GetTransfer. After that, getting around Koh Samui is the ring road, and getting to Koh Samui is the flight versus the ferry.
Get the Airalo Thailand eSIM Get the Saily Thailand eSIM Get the Yesim Thailand eSIM
FAQ
What is the best eSIM for Koh Samui?
For a week, Airalo’s 5 GB plan at US$7 for 7 days. It uses True and AIS, and the package says the cover includes Koh Samui. Saily is cheaper if you only need 1 GB (US$2.99 for 7 days). Yesim is a 30-day option, with 10 GB at US$13.20.
Does Airalo work on Koh Samui?
Airalo’s Thailand operator note, read 27 Oct 2026, says the eSIM covers the mainland and islands, including Koh Samui, on True and AIS. It is data-only 5G. The package starts when you first connect.
Is Saily cheaper than Airalo for Thailand?
For a tiny plan, yes. Saily’s 1 GB for 7 days is US$2.99, and its 3 GB for 30 days is US$5.99. Airalo’s 5 GB for 7 days is US$7, and its 10 GB for 30 days is US$11. Saily’s page does not name Koh Samui. Airalo’s does.
Can I use a hotspot?
Saily says hotspot is unlimited with no restrictions. Airalo and Yesim did not state a hotspot rule on the pages I could read on 27 Oct 2026. A local tourist SIM is the straightforward hotspot if the eSIM line is unclear.
Should I buy a local SIM in Koh Samui instead?
If the phone has no eSIM, or you want a Thai number, yes. AIS and True sell tourist SIMs and a passport is required to register one. I am not printing a price. The AIS tourist page was in maintenance on 27 Oct 2026. It is not an affiliate link.
Do I need mobile data at Koh Samui Airport?
You want it before you leave the terminal. Grab and a pre-booked driver are much calmer with a connection. The airport has Wi-Fi. The airport transfer guide covers the taxi counter and the pre-booked cars.
