If you are planning to visit Japan from Thailand and haven’t been suckered into buying an eSIM yet, I highly recommend buying a roaming package from DTAC/TRUE (AIS also has similar plans, but I haven’t tried them). The main reason is that it’s much cheaper, but also because I saw many travelers struggling with SIM cards/eSIMs purchased from both vending machines in Japan and online. In the space of one week, I saw at least five people complaining about weak coverage or spotty connectivity.
The DTAC package we chose also came with free travel insurance for a week, which is great, but very difficult to actually find on the DTAC site/mobile app. The DTAC site now directs through the TRUE roaming website (because of the merger last year), but I’m leaving this reference here because we have students going to Japan later this month.
This is the package we chose for a ten day trip, which probably has enough data if you’re not addicted to TikTok (hint, hint, daughter):
And this is what you need to click on to begin the process of registration for the free health insurance from Dhipaya Co. The process will include registering your phone number, filling out online forms, and running a special USSD code.
The graphics for the roaming packages also have English translations, but the insurance one does not. I’m not sure if the insurance is intended mainly for Thai nationals or not, but it accepted the ID number from my pink Thai ID card (it did not accept my passport number).
IMPORTANT NOTE #1: One thing to look out for regarding the insurance is that the coverage is only for a week, and it starts on the day you register for it. So you should register it just before you depart from Thailand.
IMPORTANT NOTE #2: You have to apply for the roaming packages within Thailand.
Once you land, the international roaming should activate automatically. If it does not, you can try switching the Roaming setting on your phone on and off. The coverage in Japan is provided by several carriers. In Osaka, it seemed to mostly be the KDDI network. On the train from Nara, I saw it switch to other networks (maybe DoCoMo or SoftBank – I was sleepy and reminiscing on salaryman/bartender train rides between Tenri and Miyakojima).