eSIM vs local SIM vs roaming: what to use in Asia

The three options in a nutshell

• Travel eSIM: a data profile you buy online and install on your phone before departure. No card to insert, no shop to find when you land.
• Local SIM: a line from a local carrier, bought in the country (airport counter, store, authorised dealer). It usually comes with a local number.
• Roaming: you keep using your home line abroad. Nothing to install, but outside the EU your carrier's own terms apply.

Side-by-side comparison

Local SIMs: expect to show your passport

Several Asian countries require mobile subscribers to register their identity. Here is what the rules we could verify say:

• Thailand: since 16 May 2026, an NBTC notification requires foreigners to verify their identity primarily with a passport, in person at a branch or authorised dealer, with a cap of three SIM cards per person per carrier.
• Vietnam: Decree 163/2024 says foreigners register a mobile line with a passport valid in Vietnam (under their visa or their visa-free stay period) or with an electronic identification account.
• Japan: the Mobile Phone Improper Use Prevention Act requires voice carriers to verify the customer's identity when signing a contract, prepaid lines included.

For South Korea we did not find a clear official rule for visitors, so check with the carrier before relying on a local SIM there.

Roaming: what roam like at home covers, and what it doesn't

Under the EU's roam-like-at-home rule, you use your plan at domestic rates when travelling in another EU country or in the European Economic Area (Iceland, Liechtenstein, Norway). The European Commission states that other countries are not covered, so Thailand, Japan, South Korea and Vietnam fall under your carrier's own prices, which the Commission warns can be expensive.

Some carriers do include a few non-EU destinations in their plans. Before you go, check your account to see whether your destination is included and on what terms. If you are on a non-EU carrier, the same advice applies: read your plan's international terms.

When to pick which

A local SIM is still the better choice if:

• you need a local number (local calls, bookings or services that ask for a number in that country);
• you are staying longer than travel plans run, which is roughly 1 to 30 days depending on the country;
• your phone doesn't support eSIM or is locked to a carrier.

Roaming is enough if your destination is included in your plan, you barely use data, or you are on a short layover. For everything else, a data-only travel eSIM saves you the queue on arrival and surprises on your bill.

Install the eSIM before you leave, on Wi-Fi, and don't delete it: a deleted profile can't be reinstalled. When you land, turn on the eSIM line and its data roaming, keep your usual line on for bank texts, but switch off its mobile data abroad to avoid charges from your carrier.

Keeping your number for bank texts

On a dual-SIM phone only one line uses mobile data at a time, but both numbers can receive calls and texts (that's how Apple describes it for iPhone). In practice:

1. Check compatibility: dial *#06#. If an "EID" number appears, your phone supports eSIM. It must also be unlocked (see /compatibility).
2. Install the travel eSIM at home, on Wi-Fi.
3. On arrival, set the eSIM line as your mobile data line and turn on its data roaming.
4. Leave your usual line on for calls and texts, with its mobile data and data roaming turned off.

Frequently asked questions