How Connectivity Works in Southeast Asia: Thailand, Vietnam, Indonesia
Thailand, Vietnam and Indonesia all have fast, cheap mobile networks. What differs is how hard each one makes it to get onto them. All three require passport registration before a local SIM will work, and Indonesia additionally gates your handset, not just your SIM, through IMEI registration. A travel eSIM bought in India connects as an inbound roamer instead, which sidesteps the counter in all three countries. The details that actually matter are the fair usage caps, and they're different in each.
Southeast Asia looks like one connectivity problem and behaves like three. Data is inexpensive across the region and 4G reaches further than most Indian travellers expect, so nobody has a coverage problem. What people have is an admin problem, and it shows up differently in each country. Here's what to know before you land.
The three countries are not the same problem
| Country | Network reality | The friction |
|---|---|---|
| Thailand | Excellent. 5G across Bangkok, Phuket, Chiang Mai and the islands | The mildest of the three. Passport registration at the counter, and a queue at Suvarnabhumi that peaks with the India arrivals |
| Vietnam | Very good and very cheap, strong through Hanoi, Da Nang and Ho Chi Minh City | Passport registration is enforced, and buying from an unofficial seller can leave you with a SIM that never activates |
| Indonesia | Good in Bali, Jakarta and Java. Thinner on smaller islands | Two gates rather than one. Your SIM needs registering and so does your phone |
Indonesia gates your handset, not just your SIM
This is the part almost nobody plans for. Since 2020 Indonesia has run a national device register, and phones whose IMEI isn't on the approved list are blocked from local networks. It works at the point your phone tries to attach, before your plan is even consulted, which is why a blocked handset looks to its owner like a broken SIM. Switching operators changes nothing, because the block is national rather than per-network.
For a tourist buying a local SIM, an official Telkomsel or XL store handles the registration with your passport, and the phone works for up to 90 days. Buy from a convenience store instead and staff often can't complete passport registration at all, so you walk out with a SIM that won't activate.
Why roaming avoids this entirely
Indonesian customs guidance is clear that inbound roamers using a foreign SIM don't need customs IMEI registration. A travel eSIM connects through partner networks as exactly that, so the device register never becomes your problem. It's the single strongest practical argument for sorting Indonesia before you fly rather than at Ngurah Rai.
What "unlimited" means in each country
Every unlimited plan in this region has a fair usage policy, and they work differently enough to change which plan you should buy. These are the current Matrix terms.
| Country | Fair usage | What that feels like |
|---|---|---|
| Indonesia | 3 GB per day at full speed, then 128 kbps for the rest of the day | 128 kbps carries WhatsApp text and little else. If you post reels from Bali daily, a fixed-data plan serves you better |
| Vietnam | Data stops after 5 GB in a calendar day, and resets the next day | A harder stop than throttling, but a more generous daily allowance. Plan your uploads for the morning |
| Thailand | Fair usage applies, and hotspot is restricted on some unlimited plans | If you need to tether a laptop, take the 50 GB fixed plan rather than unlimited |
The general rule across all three: unlimited buys you freedom from counting, not freedom from limits. For heavy uploaders and anyone tethering, a large fixed-data plan is usually the better product.
Two Vietnam-specific things to know
There's a purchase window. The Vietnam eSIM must be bought no more than 10 days before the date you intend to use it. Buying six weeks ahead as part of your trip planning will cause problems, which is the opposite of the advice for most destinations.
Validity runs 7, 15 or 30 days, so match it to your actual trip rather than rounding up. A twelve-day Hanoi to Hoi An to Ho Chi Minh City run needs the 15-day plan, not the 7.
Thailand is the straightforward one
The Thailand eSIM runs on DTAC at 5G or 4G, with hotspot allowed on the fixed-data plan. Coverage is strong enough that the interesting question isn't whether you'll have signal, it's which coast you're on.
December through March, the Andaman side around Phuket and Krabi is dry while the Gulf side around Koh Samui is in its wettest stretch. That affects your trip more than your network does, and ferry crossings between islands are where you'll actually lose signal. Download offline maps before boarding.
One plan or three?
Plenty of Indian itineraries hit two or three of these countries in a fortnight. The decision is straightforward.
| Your trip | Buy | Why |
|---|---|---|
| One country, one to two weeks | The single-country plan | Better value per GB, and the local fair usage terms are clearer |
| Two or more countries in one trip | The five-country Southeast Asia eSIM | Indonesia, Malaysia, Singapore, Thailand and Vietnam on one profile. Nothing to reinstall at a border |
| A long stay in one country plus a short hop | The single-country plan, plus a small one for the hop | Two profiles is easy to manage and often cheaper than one large regional plan |
Plans and prices
| Plan | Network | Price |
|---|---|---|
| Thailand: 50 GB, 10 days | DTAC, 5G/4G | ₹949 |
| Thailand: Unlimited, 10 days | DTAC, 5G/4G | ₹999 |
| Vietnam eSIM | 5G/4G, 7, 15 or 30 days | From ₹999 |
| Indonesia: 10 GB, 10 days | Telkomsel, XL, Indosat | ₹1,299 |
| Indonesia: Unlimited, 7 days | Telkomsel, XL, Indosat | ₹1,499 |
| Indonesia: Unlimited, 15 days | Telkomsel, XL, Indosat | ₹2,499 |
| Five-country Southeast Asia eSIM | Indonesia, Malaysia, Singapore, Thailand, Vietnam | From ₹1,299 |
The Indonesia plan is worth a note. It draws on Telkomsel, XL and Indosat rather than a single operator, which matters once you leave Bali and Java for smaller islands where coverage is patchier and one network's gaps aren't another's.
What you'll want working on arrival
- Grab is the default ride and food app across all three countries, and it needs data to book. In Indonesia, Gojek is the local rival and often cheaper
- Zalo is Vietnam's dominant messaging app. Hotels, drivers and tour operators frequently use it instead of WhatsApp
- Offline maps for Bali, the Thai islands and the Vietnamese coast. Ferries and mountain passes are the real coverage gaps in this region, not the cities
- QR payments. Thailand's PromptPay and Indonesia's QRIS are everywhere, and both need a live connection at the till
Before you fly
| Do this | Why |
|---|---|
| Dial *#06# and confirm an EID appears | No EID means no eSIM |
| For Vietnam, buy within 10 days of your travel date | The purchase window is a plan condition, not a suggestion |
| Match plan validity to trip length, not to the nearest round number | Vietnam runs 7, 15 or 30 days. Thailand runs 10 |
| Turn data roaming ON for the eSIM, OFF for your Indian line | A travel eSIM roams by design. Without that toggle you get signal and no data |
| Install BOTIM-style local apps and offline maps at home | Zalo for Vietnam, Gojek for Indonesia, maps for everywhere |
| Check whether your plan allows hotspot before relying on it | Allowed on fixed-data plans, restricted on some unlimited ones |
Sort it before the counter
Three countries, three sets of paperwork, and none of it necessary if the profile is already on your phone when you land.
Browse Matrix eSIM plans by destination →
- Single-country plans for Thailand, Vietnam and Indonesia, plus a five-country regional plan
- Indonesia draws on Telkomsel, XL and Indosat rather than one operator
- Hotspot allowed on fixed-data plans, so a travel partner can share
- Instant QR delivery by email or the GoMatrix app after KYC
- Your Indian SIM stays in the phone for OTPs and WhatsApp
- Support on +91 9811188888, live chat and WhatsApp
Read next
- Best eSIM for Thailand in 2026
- Best Countries to Visit Without a Visa
- 11 Best Places to Visit in December in the World
- All Matrix eSIM plans by destination
Frequently asked questions
Do I need to register my phone's IMEI in Indonesia?
Not if you're travelling on international roaming or a travel eSIM, which connects as an inbound roamer. Indonesian customs guidance says inbound roamers using a foreign SIM don't need customs IMEI registration. If you buy a local Indonesian SIM, an official operator store registers the device against your passport, and that covers you for up to 90 days.
Why did my phone stop working in Indonesia?
If you're on a local SIM and the phone has dropped off the network, the usual cause is the IMEI register rather than the SIM. The block applies nationally, so buying a different local SIM won't fix it. Travel eSIMs avoid the issue because they connect as roamers.
Does unlimited really mean unlimited in Southeast Asia?
No, and the terms differ by country. Indonesia gives 3 GB a day at full speed then drops to 128 kbps. Vietnam stops data after 5 GB in a calendar day and resets the next day. Thailand applies fair usage and restricts hotspot on some unlimited plans. For heavy uploading or tethering, a large fixed-data plan usually works out better.
How early can I buy a Vietnam eSIM?
No more than 10 days before your intended date of use. That's unusual, since most destinations reward buying early, so add it to your pre-trip list rather than sorting Vietnam alongside your flights.
Which network does each plan use?
Thailand runs on DTAC. Indonesia draws on Telkomsel, XL and Indosat, which helps once you're off Bali and Java. The Vietnam plan runs at 5G or 4G with validity options of 7, 15 or 30 days.
Do I need three separate plans for a three-country trip?
Not necessarily. The five-country regional plan covers Indonesia, Malaysia, Singapore, Thailand and Vietnam on one profile, so nothing needs reinstalling at a border. Single-country plans give better value per GB if you're only visiting one.
Can I share my connection with a travel partner?
Yes on the fixed-data plans, which allow hotspot. Some unlimited plans restrict it under fair usage rules, so if tethering matters, check before you buy rather than after.
Will my Indian number still work?
Yes. The eSIM adds a second line rather than replacing your Indian SIM, so bank OTPs keep arriving. Keep data roaming off on the Indian line and on for the eSIM.
How much data do I need for two weeks in Southeast Asia?
Around 10 to 15 GB for a typical traveller using maps, Grab, messaging and photo sharing. Go higher if you post video daily, since uploads are the difference between a comfortable plan and running dry on day nine.
Where will I actually lose signal?
Ferries, mountain passes and the smaller Indonesian islands. Cities in all three countries are well covered. Download offline maps for each place before you set off, particularly before island crossings.
