How to convert your physical SIM to an eSIM in Thailand
An overview of turning your existing number into an eSIM through your carrier: what to prepare, what happens to the old SIM, and how it differs from buying a data-only travel eSIM.
Quick answer
- Converting your existing number to an eSIM has to go through your own carrier, whether through its app, a store, or an online channel. Steps, documents and terms differ between carriers (AIS, True, dtac) and can change, so always check your carrier's official channels first.
- This is not the same as buying a travel eSIM. Our travel eSIM is data-only, adds no new number, and does not change your existing one. Keep your home SIM active for OTP codes. If you want to convert, do it before travelling, not at the airport.
Two things with similar names that are not the same
When people search for how to change a SIM to an eSIM, they usually mean one of two things. The first is moving the number you already use from a physical SIM card to an eSIM profile with the same carrier. The second is adding another eSIM just for mobile data when you travel abroad. Both use the same technology, but they go through different channels and give different results.
| Topic | Convert your SIM with your carrier | A data-only travel eSIM |
|---|---|---|
| Your number | Your existing number carries over | No number; data only; your existing one is unchanged |
| Where you do it | Through your own carrier (app, store or online, as the carrier offers) | Buy on the web, no app, receive a QR code by email |
| What happens to the old SIM | Generally the old card is replaced; confirm the details with your carrier | Your home SIM keeps working as normal, since this adds a second line |
| Best suited to | People who want their usual number on an eSIM | People travelling abroad who need mobile internet |
The two compared
What needs to be true before you can convert?
Almost every carrier needs the same basics: a phone that supports eSIM and is not network-locked. Other conditions, such as plan type, number status or the registered holder, depend on each carrier's policy and may change.
- A phone that supports eSIM. You can check the model with our device checker.
- A phone that is not network-locked, or is allowed to use that carrier's profile, especially if it was bought on instalments or with a plan.
- A number that is still active and registered in the way your carrier requires.
- An operating system version the carrier supports. Update before you start.
Which channels exist, and what should you bring?
Conversion goes through your own carrier only. We do not do it for you, and this page does not list any carrier's steps. Channels a carrier may offer include its app, a store branch, or an online or USSD service. Carriers offer different channels and change them over time, so look at the official channels of AIS, True or dtac directly.
- Your ID card, or passport for foreign residents, as your carrier requires for identity verification.
- The phone you will put the eSIM on, with enough battery.
- A stable Wi-Fi connection, since downloading an eSIM profile needs internet.
- Your current SIM card, in case the carrier asks for it or for details printed on it.
- A backup email or number for verification codes, in case your main number is briefly unavailable during the process.
What happens to the old physical SIM?
Generally, one number is tied to a single profile at a time. Once the eSIM is active, the old SIM card is usually deactivated or replaced, though carriers handle it differently. Ask clearly whether the old SIM will still work, and what you would do to go back to a physical SIM.
- Do not throw away or cut up the old SIM until you are sure the eSIM handles calls and SMS properly.
- If you change phones, moving the eSIM to the new phone has to be arranged with the carrier again under that carrier's terms.
- If the phone is lost or broken, recovering a number held on an eSIM means contacting the carrier, so note down its contact channels.
Do it before you travel, not at the airport
Converting to an eSIM may involve identity verification, waiting for activation, and sometimes sorting out small snags. If you do it on the day you fly, you risk having no working number at the moment you need it most, such as when contacting a hotel or receiving a bank OTP. Do it several days ahead, and test calls, SMS and OTP before you leave.
- 1Check the phone and updateConfirm the phone supports eSIM and is not locked, and update to the latest system version.
- 2Look up your carrier's channelOpen the official app or website of AIS, True or dtac to see which channel is offered and what documents are needed.
- 3Follow the carrier's stepsFollow what the carrier specifies, on stable Wi-Fi, and keep proof of the request.
- 4Test the number fullyMake a call, receive one, send and receive SMS, and receive an OTP from your bank app or other services you use often.
Should you keep your home SIM active when you travel?
Yes, keep your main number reachable, especially if it receives bank OTPs or verifies your accounts. Our travel eSIM is data-only, with no number and no calls or SMS, so it does not replace your existing number; it adds internet. Your existing number stays in place and can receive OTPs under your carrier's terms.
| Situation | What to consider |
|---|---|
| You must receive bank OTPs abroad | Ask your carrier how SMS roaming works and whether it costs anything, and keep the home line on, with data roaming off for that line. |
| You want mobile internet abroad | Buy a travel eSIM for the destination. Check the live price on the plan page. |
| Your phone has eSIM plus one physical slot | The physical slot can hold your main number while the eSIM holds the travel eSIM, giving you two lines at once. |
Keeping the home SIM
Can you add a travel eSIM after converting your own number?
Generally yes, if the phone supports multiple eSIM profiles. How many it can store and how many can be active at once varies by model, so check the manufacturer's guide. On most dual-SIM phones, keep the main line for calls and SMS and set the travel eSIM line as the data line.
How to install a travel eSIM with a QR code is in our install guide, and if you are unsure how an eSIM differs from a virtual SIM or a prepaid plan, see our virtual SIM and prepaid eSIM explainers.
Common mistakes when converting a SIM
- Leaving it to the day of the flight, which risks having no working number when you need it.
- Trying it on an unstable or public Wi-Fi network, so the profile fails to download.
- Discarding the old SIM before testing, when you are not yet sure calls and SMS work.
- Assuming a travel eSIM is a number change, when it is data-only and has no number.
- Leaving data roaming on for the home SIM, risking unintended roaming charges. Set the cellular data line to the travel eSIM.
FAQ
Where do I convert my SIM to an eSIM?+
Through your own carrier, such as AIS, True or dtac, using whichever channel it offers, for example its app, a store or an online service. Channels and terms can change, so check your carrier's official channels.
What should I bring?+
Generally your ID card or passport as your carrier requires, a phone that supports eSIM and is not locked, and a stable Wi-Fi connection. Check the exact list with your carrier before you go.
What happens to my old SIM card?+
Generally a number is tied to one profile at a time, so the old SIM is usually replaced or deactivated when the eSIM goes live. Carriers differ, so ask yours clearly before you start.
Can I do it at the airport before my flight?+
It is not recommended, since you may need identity verification and have to wait for activation. Do it several days ahead and test calls, SMS and OTP before you leave.
Is your travel eSIM the same as converting my SIM?+
No. Our eSIM is data-only, with no number and no calls or SMS, and it does not change your existing number. You buy it on the web and receive a QR code by email.
Should I keep my home SIM when I travel?+
Yes, keep your main number, especially if it receives OTPs, and use the travel eSIM as the data line. Turn off data roaming on the home SIM to avoid unintended charges, and ask your carrier about SMS roaming.
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