Internet for Thailand, Vietnam and Cambodia: one eSIM or several?

A classic Southeast Asia loop looks like this: Bangkok, a few islands, a flight or bus into Cambodia for Angkor, then Vietnam from south to north. Three countries, three different mobile networks, and a very real temptation to buy a local SIM at every border.

You do not have to. With VoaSim you enter the countries and dates in the price simulator and get one eSIM that covers the whole route, with unlimited data and one flat price per duration.

One eSIM for the three countries: how it works

VoaSim sells travel eSIMs for 170 destinations across every continent, including Thailand, Vietnam and Cambodia. In Europe, one single plan covers 50 countries. Outside Europe the logic is the same in practice: you type your countries into the simulator and VoaSim issues the regional product that covers your full route, so you install once and stop thinking about it.

What you get is data only. There is no phone number and no traditional voice line, but WhatsApp, Telegram, FaceTime, Google Maps, Grab and Gojek all run over data on your own number, because your physical SIM stays in the phone. The only thing you switch off is your home carrier's data roaming.

Data is truly unlimited: no cap, no throttling after a certain point, no hidden fair-use clause. That matters on a trip where you will be streaming maps, translating menus and uploading photos from a night bus.

Price for a Thailand + Vietnam + Cambodia trip

One price per duration, the same for every destination. Today's table includes the 15% promo:

Most three-country itineraries land between 15 and 30 days, so USD 42.90 or USD 61.90 covers the whole trip. Trips of 1 to 4 days pay the 5-day package, and the maximum per eSIM is 90 days. Travelling as a couple? A second eSIM in the same order gets 10% extra off. Payment is by international credit or debit card in USD through Stripe, with an invoice by email.

Coverage: Bangkok, the islands, Angkor and the Vietnamese coast

In Thailand the eSIM connects automatically to local networks such as AIS, True and Dtac, picking whichever gives the best signal where you stand. Expect 5G in central Bangkok and solid 4G in Phuket, Chiang Mai, Krabi and Koh Samui. In Cambodia and Vietnam the same automatic selection applies with local partners, so Siem Reap, Phnom Penh, Ho Chi Minh City, Hoi An and Hanoi are well served.

Two honest caveats. On island-hopping boat trips in open water the signal drops in and out, the same as with any local SIM. And remote mountain sections, Ha Giang loop passes or jungle temple areas outside the main Angkor circuit, can go quiet for a while. That is coverage reality, not an eSIM fault. See our destination pages for more detail per country.

Today's prices

Today's promo prices (15% off), the same for every destination. Second eSIM in the same order: 10% extra off. Trips of 1-4 days use the 5-day package.

Border crossings and flights between countries

This is where a single eSIM earns its money. With local SIMs you buy one in Bangkok, another at Poipet or Siem Reap airport, another in Saigon, and each one means a shop, your passport for registration, and popping your home SIM out of the tray.

With VoaSim the profile stays installed. When you cross from Thailand into Cambodia by land, or fly Siem Reap to Ho Chi Minh City, the eSIM simply searches for a new network on arrival. If it takes a minute, toggle airplane mode on and off. If it still will not connect, use the free eSIM Rescue tool, which diagnoses an eSIM of any brand with no signal, or message human support.

Practical tip: download offline maps for each city before you leave your hotel Wi-Fi. Not because you will lack data, but because land border zones and long bus routes can be slow, and an offline map loads instantly.

Install before you fly, start counting when you land

The QR code arrives by email within minutes of purchase, and you get a WhatsApp heads-up if you left a number at checkout. Install it at home, on Wi-Fi, following the step-by-step guide for iPhone and Android.

Your days start counting at the eSIM's first connection to a network at the destination, not at purchase. So install early but keep the eSIM line switched off until your plane doors open in Bangkok. On Android in particular, do not turn on the eSIM's mobile data before the trip.

Compatibility: iPhone XR or newer, Samsung Galaxy S20 or newer, Google Pixel 3 or newer, and most phones released from 2020 on. Universal check: dial *#06# and look for an EID. Carrier-locked phones must be unlocked first. VoaSim does not sell physical SIM cards. More on this in our guides.

When another option might suit you better

Be fair to the alternatives. If you are a very light user who only needs maps and messaging for a week, a GB-based eSIM from brands like Airalo, Nomad, Saily or Ubigi, sold per gigabyte in their apps, can come out cheaper. Check the cap, the validity window and the tethering rules in each one's terms.

If you rely on a hotspot to work from a laptop, do not assume it. With VoaSim, tethering depends on the plan, so ask support before you build your trip around it. Other unlimited providers, such as Holafly, describe their own usage and tethering conditions in their terms; read them.

Carrier roaming (T-Mobile, AT&T, Verizon, EE, Vodafone, Telstra and friends) is the simplest option of all if your plan already bundles Asia, though daily allowances and post-allowance speeds vary, so check the current rate in your carrier app. Compare approaches on our roaming page.

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