Phone settings before going abroad, and how to switch off your Thai SIM while away
A pre-flight settings walk-through for iPhone and Android: per-line roaming, choosing the data line, turning the Thai SIM fully off or keeping it for OTP, background data, updates, offline maps and Find My.
إجابة سريعة
- Before flying, set three main things: choose your eSIM or foreign SIM as the mobile data line, turn off data roaming on your Thai SIM, and manage background data and updates. For the Thai SIM you have two modes: switch the line off entirely to avoid charges, or keep it on only to receive SMS OTP with data roaming turned off.
- Menu names differ by model and system version, so treat the tables here as a guide, find the matching item on your own phone and check roaming terms with your Thai operator.
Overview: what to set before you leave
The aim is for data to flow through the line you chose, not through Thai SIM roaming by accident, for the phone not to burn background data needlessly, and for you to stay reachable and able to locate your phone if something happens. Follow the sections below in order. It does not take long, and it is best done while you still have home Wi-Fi.
- Data line and roaming: lowers the risk of accidental charges.
- Background data and updates: saves data and battery.
- Offline maps, documents and Find My: help when you are offline or lose the phone.
iPhone settings before going abroad
iPhones that support eSIM usually separate settings per line, so you can turn data roaming off for the Thai SIM line and on only for the eSIM line. The menus sit under the mobile network settings, but they may differ by iOS version.
| الإعداد | How to approach it on iPhone |
|---|---|
| Label each line | Give each line a clear label, such as Thai and Travel, so you do not pick the wrong one. |
| خط بيانات الجوال | Select the eSIM line for mobile data, and turn off any option that lets data switch lines automatically, so data does not drift to the Thai line. |
| تجوال البيانات لكل خط | Turn data roaming off for the Thai line and on for the eSIM line if the plan says so. |
| الاتصال عبر Wi-Fi | Check whether your Thai operator supports it and how it is charged. See our guide to calls, SMS and OTP while abroad. |
| Find My | Check that Find My is on and last-location sending is enabled before you fly. |
iPhone pre-trip settings
Android settings before going abroad
Android brands have different menu layouts, but the principle matches iPhone: choose the data line, turn roaming off on lines you do not use, and limit background data. Open your phone's SIM and mobile network settings and look for the item that matches the table below.
| الإعداد | How to approach it on Android |
|---|---|
| Active SIMs and eSIMs | See the SIM list in the SIM or connections menu, label each line and choose the data line. |
| تجوال البيانات | Turn roaming off for the Thai line and on for the eSIM line as the plan states. Some models split by line and some have one switch, so check on your phone. |
| Background data | Restrict background data for non-essential apps and enable a data saver mode if available. |
| Automatic updates | Set app and system updates to run on Wi-Fi only. |
| Find my device | Check that your system's find-my-device service is on and linked to the right account. |
Android pre-trip settings
Turning off your Thai SIM abroad: fully off, or kept for OTP
Turning off your Thai SIM can mean two different things: turning off data roaming (the line can still attach to a network and receive SMS) or turning the line off entirely (it receives nothing). Which one you pick depends on whether you need to receive OTP from a bank or an important app.
| الوضع | Suits when | احذر من |
|---|---|---|
| Data roaming off, line on | You need to receive SMS OTP or important calls from Thailand. | Receiving calls and SMS while roaming may be charged under your operator's terms. Check with your Thai operator. |
| Thai line switched fully off | You do not need OTP or calls from Thailand and want to cut the charge risk as far as possible. | You will not receive OTP, so set up another verification method before flying, such as your bank's app. |
Two ways to turn the Thai SIM off
Step-by-step setup
- 1Install the eSIM on Wi-FiFollow our how-to-install-eSIM guide and label the new line clearly.
- 2Choose the mobile data lineSet the eSIM as the data line and turn off automatic data switching if there is such an option.
- 3أطفئ تجوال البيانات على الشريحة التايلانديةTurn it off only for the Thai line, and enable roaming on the eSIM line if the plan says so.
- 4Manage background dataRestrict non-essential apps, set updates to Wi-Fi only and turn off cloud backups over mobile data if you do not need them.
- 5Download offline maps and documentsDownload maps of your destination and keep tickets and lodging details in a form you can open offline. See our offline maps and navigation guide.
- 6Test before leaving homeToggle airplane mode, then check the data line is still the eSIM and see whether any roaming indicator appears.
Updates, apps and background data
Many systems and apps update or sync in the background, which can use a lot of data unnoticed. Run big updates at home before flying and set automatic updates to Wi-Fi only. A data saver mode adds another layer. Real usage depends on which apps you have, so use the data calculator to estimate.
- Turn off automatic photo and video upload to the cloud over mobile data if you do not want it.
- Turn off video autoplay in social apps.
- Check apps that use location or sync all the time, and limit them to when the app is open.
Backups, screen lock and preparing for a lost phone
- Back up key data at home on Wi-Fi and check that your screen lock and main-account verification are on.
- Note down your IMEI and keep it apart from the phone. See our guide to checking EID and device identifiers.
- Read the steps for a lost or stolen phone abroad in advance.
- If you have insurance, check whether devices are covered, with the insurer directly.
الأسئلة الشائعة
الأسئلة الشائعة
What should I set on my iPhone before going abroad?+
Choose the eSIM line for data, turn off data roaming for the Thai line, limit background data, set updates to Wi-Fi only, download offline maps and check that Find My is on.
Is the Android setup before travel different from iPhone?+
The principle is the same but menu names differ by brand and version. Open the SIM and mobile network menu and look for the item that matches the table above.
How should I turn off my Thai SIM abroad?+
If you need OTP, turn data roaming off but keep the line on. If you need nothing from Thailand, turn the line off entirely. Check call and SMS roaming terms with your Thai operator.
If I turn the Thai SIM fully off, can I still get bank OTP?+
Usually not, if OTP is sent by SMS. Set up another verification method in your bank's app before flying, or keep the line on with data roaming off.
Do I need to keep airplane mode on all the time?+
No. Airplane mode cuts mobile signal and may cut Wi-Fi unless you re-enable it. Use it on the plane or when you want to cut signal temporarily.
Should I update my phone before the flight or after arrival?+
Run big updates at home on Wi-Fi before the flight so they do not eat data at the destination, and set automatic updates to Wi-Fi only.
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