How to set up a Japan eSIM before leaving Thailand, and what to switch on after landing
A start-to-finish order of work, from checking your phone supports eSIM to what to do at Narita, Haneda or Kansai, plus fixes for no-signal problems.
快速解答
- Install the eSIM over Wi-Fi in Thailand before the flight, but leave the line switched off until you reach Japan.
- Keep your Thai SIM on to receive bank OTP texts, with its mobile data and roaming turned off to avoid surprise charges.
- After landing, select the eSIM as your mobile data line, turn on data roaming for that line, and wait for a Japanese network to appear.
Step 1: check support and the carrier lock
Not every phone supports eSIM, and a handset locked to a Thai carrier may refuse a foreign profile. Check both points before you buy a plan, because a failed install close to departure day is stressful.
The check takes only minutes, yet a problem found on departure day is far harder to fix. Do it a day or two ahead, and keep the seller's order email or page saved on the phone in case you need to contact support.
- iPhone: open Settings > General > About, look for an EID number, and check that Carrier Lock says no SIM restrictions.
- Android: usually Settings > About phone > Status shows an EID; menu names differ by brand.
- If you are unsure about a carrier lock, ask your current provider before buying.
Step 2: install over Wi-Fi in Thailand
Install on a stable home or office Wi-Fi connection, since the profile has to download. Do not delete the profile afterwards, because most QR codes cannot be reused. The general install flow is covered in our install guide.
- 1iPhone: scan the QR code or use the seller's appGo to Settings > Cellular > Add eSIM and scan the QR code the seller sent. If the email offers an install button, follow it as instructed.
- 2Android: add the SIM from the network menuGo to Settings > Network & internet > SIMs > Add eSIM, then scan the QR code or enter the details manually. Some models word the menus differently.
- 3清楚標示各條門號Rename the lines Thai SIM and Japan eSIM so you never pick the wrong one when changing data settings.
The Thai SIM and bank OTPs: what to set
Many Thai banking apps send OTPs by SMS to your Thai number, so keep that SIM on but stop it using data. Receiving a text normally does not need mobile data, though call and SMS terms while roaming depend on your Thai provider, so check with them.
| 設定 | Thai SIM | 日本 eSIM |
|---|---|---|
| Line on | 開啟 | On after landing |
| 行動數據 | 關閉 | On, set as main data line |
| 數據漫遊 | 關閉 | 開啟 |
| Wi-Fi 通話 | Optional, if your carrier supports it | 不適用 |
Travel day: what to switch on, and when
- At the Thai airport: join airport Wi-Fi, confirm the eSIM profile is still there, and download offline maps.
- On the plane: use airplane mode and keep the eSIM line off.
- After touchdown: turn off airplane mode, switch on Japan eSIM, set it for mobile data, and enable data roaming for that line.
- Wait a minute or two for a Japanese network name to show in the status bar, then test a web page or map.
On arrival at Narita, Haneda or Kansai
The trip into the city is when you need data straight away: Visit Japan Web QR codes, maps and messages to friends. Thai passport holders can currently enter visa-free for up to 15 days per visit, but confirm with the official source before you travel.
- If data has not come up yet, use the airport's free Wi-Fi while you troubleshoot, but treat it as an open network and avoid banking.
- Save screenshots of your Visit Japan Web QR codes in case loading is slow.
Troubleshooting: no signal or no data
| 狀況 | 可以嘗試的做法 |
|---|---|
| 完全沒有訊號 | Toggle airplane mode, then restart the phone. |
| Bars shown but no data | Check that the eSIM is the mobile data line and its data roaming is on. |
| Will not attach to a network | Open network selection, turn off automatic mode, and pick a network the seller lists. |
| Very slow or dropping | Try another network, move to open ground and check the remaining data allowance. |
On network selection: Japan has four main operators, NTT docomo, au, SoftBank and Rakuten Mobile. Travel eSIM plans usually ride on one or two of them. If automatic mode cannot find a signal in a given spot, switching by hand to a network the plan supports often helps, so check which networks your plan uses.
On APN: most plans configure it automatically. If the seller tells you to enter it by hand, copy the values exactly. If that still fails, contact the seller's support with screenshots.
常見問題
常見問題
Can I install the eSIM after landing in Japan?+
It works if you have Wi-Fi, but it is not recommended: airport networks can be slow and need registration. Installing in Thailand first is easier.
Do I need to turn the Thai SIM off completely?+
No, and you should not if you expect OTP texts. Keep the line on but turn off its mobile data and roaming.
What should I try first if there is still no data?+
Check the data line and the eSIM's data roaming, then toggle airplane mode and restart, before selecting a network manually.
Can I use the phone as a hotspot?+
It depends on the plan; some limit or block tethering, so read the plan terms before buying.
About the author
Porsch Kunnipat Siramanakul
- Co-founder of eSIMonline.asia
- Digital marketer
- Performance marketing and marketing planning
Instagram 和 TikTok 沒有網頁分享按鈕，因此我們會改為開啟手機的分享選單，或直接複製連結。