In short: To travel to Thailand (Bangkok, Phuket and the islands) the eSIM keeps you connected as soon as you land in Suvarnabhumi, without queues or exorbitant roaming charges. AIS and True coverage extends well across the classic tourist route, although in remote beaches, ferries, and some Bangkok alleys, the signal can drop. Activate it before leaving Spain.
Bangkok, Phuket, and the southern islands form the route where almost everyone begins their trip to Thailand: you land in Suvarnabhumi or Don Mueang, spend a few days in the capital, head down to the Andaman by plane or night bus, and hop from island to island by ferry. It's a route with a lot of movement—taxi, BTS, ferry, songthaew, moto-taxi—and connectivity behaves differently in each segment. This guide focuses specifically on that: what actual coverage you'll have at each point of that itinerary, not a generic snapshot of the entire "Thailand." If your trip leans more towards the north (Chiang Mai, Chiang Rai, the Golden Triangle), you'll find our general guide to internet in Thailand more useful, as it covers the entire country.
Coverage in Bangkok, Phuket, and the islands
Bangkok and Suvarnabhumi Airport
At Suvarnabhumi, you'll have 4G/5G coverage from the moment you exit the jet bridge. So, if you activate your eSIM before taking off from Spain, upon landing, you'll just need to open Settings → Mobile Data, and you can already order a Grab (Thailand's equivalent of Uber) without relying on airport SIM card counters, which can have long queues at certain times. Within the city, the signal is strong on the Skytrain (BTS), the metro (MRT), and in tourist areas like Sukhumvit, Silom, or Khao San Road. It does weaken inside some enormous shopping malls (like ICONSIAM or Terminal 21, with several basement floors) and in very narrow alleys—the sois—between tall buildings, where the signal bounces poorly. This isn't a serious problem, but if you're making an important video call, it's best to find an open area.
Phuket and the Andaman Coast
Phuket has good coverage in Patong, Karon, Kata, and Phuket Town itself, with stable 4G and 5G in the most populated areas. Phuket Airport also has runway coverage. However, things change on the northern beaches of the island (Mai Khao, Nai Yang) and in the more secluded southern coves, where the antenna density is lower, and 4G occasionally becomes 3G, especially during peak hours when the beach is crowded. If you're going to Krabi or Railay Beach—a peninsula only accessible by boat because it's surrounded by limestone cliffs—keep in mind there's no road access: coverage is available but weaker than in Phuket, and it's advisable to download an offline map before boarding the longtail boat.
The islands: Koh Samui, Koh Phangan, Koh Phi Phi, Koh Tao and Koh Lanta
Koh Samui is the island with the best infrastructure in the south, with almost urban coverage in Chaweng and Lamai. Koh Phangan has a good signal in Thong Sala and Haad Rin, but during the Full Moon Party, the network gets saturated with thousands of phones connected simultaneously on the same beach: it's not the eSIM failing, it's that the local tower can't handle the demand on that specific night. Koh Phi Phi, being small and car-free, has decent coverage in the village but loses signal in coves like Maya Bay as soon as you move a little further away. Koh Tao (the diving island) and Koh Lanta have more irregular coverage, especially on the western beaches of Koh Lanta, where there are still stretches with only 3G. And one detail that surprises many people: on ferry crossings between islands, the signal disappears for several minutes on the open sea, so don't count on data during the journey for work or video calls.
AIS vs True: which operator is best
Thailand has simplified its operator landscape in recent years: True and DTAC merged into True Corporation, so today, in practice, you compete between two major networks, AIS and True, instead of three. AIS typically leads in rural coverage and smaller islands thanks to its historical network of repeaters; True has invested heavily in urban 5G and performs very well in Bangkok, Phuket Town, and Koh Samui. With a data eSIM, you don't manually choose the operator: the profile connects to the associated network, and in plans that include several local partners, the phone automatically selects the one with the best signal in each area. For the Bangkok–Phuket–islands route, in practice, you won't notice much difference between AIS and True: both cover the tourist route well, and the areas where one fails are usually the same where the other also struggles (remote beaches, interior of small islands, ferries).
| Area | Typical coverage | Where it might fail |
|---|---|---|
| Bangkok (city center and BTS/MRT) | Stable 4G/5G | Basements of shopping malls, narrow sois |
| Phuket (Patong, Kata, Karon) | Stable 4G/5G | Northern beaches of the island, peak hours during high season |
| Krabi / Railay Beach | Reasonable 4G | Area without road access, only by boat |
| Koh Samui | Almost urban 4G/5G | Mountainous interior of the island |
| Koh Phangan | 4G in Thong Sala and Haad Rin | Occasional saturation during Full Moon Party |
| Koh Phi Phi / Koh Lanta / Koh Tao | 4G in the main village | Secluded coves, western beaches |
| Inter-island ferries | Variable | No signal in several stretches of open sea |
How many GB you need based on your itinerary
This depends more on what you do than on how many days you stay. If you're going to navigate with Google Maps, send photos via WhatsApp, and check Grab or Bolt to get around, a modest plan will be more than enough. If you're also going to upload 4K videos to social media from the beach or work remotely (there are quite a few digital nomads settled in Koh Phangan and Chiang Mai), you'll need significantly more data. A short three or four-day getaway to Bangkok can be managed with a small plan; a two-week Bangkok–Phuket–islands trip requires a more generous data package because maps, translations, and ferry bookings constantly consume data in the background. For the specific cost, check the current price on the PuraSIM Thailand eSIM plan: it changes according to promotions, and there's no point in giving you a figure here that might be outdated by the time you read this.
If your trip doesn't end in Thailand and you're also hopping to Singapore or Malaysia (a very common combination: Bangkok, Phuket, then Kuala Lumpur or Singapore), the regional eSIM for Singapore, Malaysia, and Thailand will be more cost-effective than buying a new plan at each border.
How to activate your eSIM step-by-step
- Purchase the plan on purasim.com before leaving Spain, calmly and with Wi-Fi at home.
- Scan the QR code you receive by email and follow the phone's installation wizard (eSIM-compatible iPhones and Androids do this in a couple of minutes).
- Do not activate the data plan yet: leave it installed but turned off until you land, so consumption doesn't start counting prematurely.
- Upon landing at Suvarnabhumi, Don Mueang, or Phuket airport, activate the plan in Settings → Mobile Data and select the eSIM as your data line.
- Verify that data roaming is enabled for that line (this is a step many people forget and then think the eSIM "doesn't work").
- If you also have your physical Spanish SIM, disable its data to prevent your phone from switching networks without warning and accidentally incurring roaming charges.
The entire process takes less time than the passport control queue at Suvarnabhumi during high season, which is where you truly lose time at that airport. If this is your first time installing an eSIM, we have a step-by-step eSIM installation guide with screenshots for iOS and Android.
What almost no one tells you
There are details about traveling to Thailand that don't appear in generic guides but do make a difference with connectivity:
- Grabbing a taxi from the airport is cheaper with active data. If you leave the terminal without a connection and go straight to the taxi drivers offering "fixed" rates at the door, you usually pay more than by ordering a car through the app with the eSIM already working from the jet bridge.
- Normal calls and SMS are not included in most data plans. To talk to your hotel or the ferry driver, use WhatsApp, Line (widely used in Thailand), or Wi-Fi calls when available; don't assume you can make a traditional call with the eSIM number.
- Songkran (the water festival in April) is tough on mobile phones. If your trip coincides with these dates, bring a waterproof case: it's not about coverage, it's about people getting their phones wet even if they keep them in their pockets.
- In Railay Beach and coves without road access, download an offline map before boarding the boat. There's no mobile phone shop to go to if you run out of data, and the signal in that specific area is the weakest on the entire route.
- The Full Moon Party crashes the local network, not your eSIM. If nothing loads that night, it's not a fault with your plan: it's because tens of thousands of mobile phones are competing for the same antenna in Haad Rin.
- For a very short weekend layover in Bangkok, consider if you really need to buy anything. If your Spanish operator already includes reasonable roaming in Southeast Asia (some plans cover it), it might be more convenient to use that for two days than to manage a new eSIM just for 48 hours. The eSIM clearly wins on trips of a week or more, where the Spanish operator's roaming charges skyrocket.
eSIM vs. roaming vs. local SIM vs. Wi-Fi
Before deciding, it's worth looking at the four options side-by-side in terms of what truly matters: what you have to do and how reliable it is.
| Option | Cost | Speed | Management |
|---|---|---|---|
| Spanish operator's roaming | Cost skyrockets outside the EU | Normal | Zero management, already works |
| Local physical SIM (AIS, True) | Cheap once in Thailand | Very good | In-store process, temporarily lose your number |
| PuraSIM eSIM | Check current price at purasim.com | Very good on Bangkok-Phuket-islands route | 100% digital, bought from Spain, you arrive already connected |
| Hotel/hostel/beach bar Wi-Fi | Free, but not your own | Very variable | Dependent on someone else's network and if it works that day |
The local SIM wins on pure price if you don't mind spending time at a phone shop right after landing, queuing, and sometimes showing your passport for registration. The eSIM wins on convenience: you buy it comfortably from your sofa at home, activate it when you get off the plane, and don't depend on finding an open shop or a salesperson who speaks English. And compared to your Spanish operator's roaming, for any trip longer than three or four days to Thailand, the eSIM is much more reasonable with most Spanish tariffs; to know exactly how much you save based on your operator, check out our comparison of eSIM versus roaming. If you've never used an eSIM before and aren't sure how it differs from a traditional physical chip, this other guide on international chip versus eSIM will clarify the basic doubts before buying.
Common mistakes travelers make on this route
The most common one: buying the plan and not installing it until arriving at the hotel, after having gone through customs, queued for a taxi, and wasted half an hour unnecessarily. Install the profile at home, with Wi-Fi, and only activate it upon landing; the installation process needs a connection, activation does not.
The second mistake is calculating GBs thinking only in "travel days" without considering that on the islands you'll use maps and location battery much more than in Bangkok, where you can navigate by metro and English signs. And the third, very typical on the Phuket-islands route: assuming you'll have coverage during the ferry ride to work or make a video call. On the open sea, don't count on it; dedicate those journeys to downloading what you need beforehand, not doing it on the fly.
If you want to maximize data consumption throughout the route—especially useful if you bought a tight plan—we have specific tricks to save data with an eSIM while traveling that are not the typical generic tips like "turn off automatic updates."
Frequently Asked Questions
Is there 5G in Bangkok and Phuket?
Yes, both AIS and True have 5G deployed in Bangkok and the most populated areas of Phuket. For a traveler's normal use (maps, messaging, social media) 4G is more than sufficient; 5G is primarily noticeable if you upload heavy videos.
Does the eSIM work on islands like Koh Samui, Koh Phangan, or Koh Phi Phi?
Yes, with good coverage in the main centers of each island. In secluded coves, undeveloped beaches, or the interior of smaller islands, the signal drops and may become 3G or disappear, so it's advisable to have the map downloaded before moving around those areas.
How many GB do I need for Bangkok, Phuket and the islands?
There isn't a single valid figure for everyone: it depends on whether you'll be working remotely, uploading videos, or just using maps and messaging. As a rough guide, a short city-focused trip consumes significantly less than a multi-week island-hopping itinerary with the map active almost all day.
Do I need a VPN in Thailand?
For a tourist's usual use, no. The services most travelers use (Google, Instagram, YouTube, WhatsApp) work without issue. If you're concerned about privacy when connecting to open Wi-Fi networks in hostels or cafes, then using one might make sense; in our guide to eSIM, VPN, and privacy when traveling we explain when it's worthwhile.
Does the eSIM work on the ferry between islands?
On open sea stretches, do not expect coverage: the signal disappears for several minutes on most journeys between Koh Samui, Koh Phangan, and Koh Phi Phi. As you approach land again, the connection will return automatically.
Can I use the same eSIM if I also go to Singapore or Malaysia?
With the specific Thailand plan, no: it's designed for the Thai network. If your itinerary includes several Southeast Asian countries, it's more convenient to get a regional eSIM that covers all three destinations without having to buy a new plan at each border.
What's the difference between this guide and the general guide to Thailand?
This guide focuses on the classic southern tourist route: Bangkok, Phuket, and the Andaman and Gulf islands. If your itinerary includes the north of the country—Chiang Mai, Chiang Rai, the Golden Triangle—the coverage and specific details change, and that part is better explained in the general guide to internet in Thailand.
