Originally Posted by
Aeolus
If you are going around several Asian countries, I highly recommend the AIS Sim2fly 4GB/8 Days Traveller Roaming. I used them in Japan, Hong Kong and Thailand and it worked on 4G data with fantastic coverage. Another plus is, you could pick these cards up on eBay or Phone shops in Hong Kong without the need to surrender your passport, an added plus as I do worry about these telco shops taking my passport details. Quite cheap too at HKD90.
All three major service providers here in Thailand offer a selection of these roaming SIMs:
The ready-to-use SIM2Fly SIM Roaming
SIM GO! Inter
https://pantip.com/topic/36302316
While I wouldn't recommend these for use in Thailand - I'd just get a standard or "Tourist" SIM, they do offer some advantages to those in Thailand, or perhaps using Thailand as a jumping off point first, for travel beyond Thailand. And you have the SIM in hand. These are used primarily for data, with voice and messaging via an app like LINE. That said, buying a local SIM is perhaps the best solution.
I've used the AIS SIM2Fly and DTAC SIM Go Inter products quite a few times, and highly recommend them.
I'd be surprised if you could activate these without proper registration, but maybe there is some sort of black/grey market for these? Whenever I buy these, and I bought three yesterday for a trip to Hong Kong and Macau, I have to show my original passport.