I lived in Thailand for several months with TMobile, data is slow but useful to have. I spend 300 baht a month for an AIS plan that provides me all the high speed data I need.
For short term travel, yes. Long term stay, no. It is against their terms, I have tried them on two different occasions and they canceled me due to using data beyond their agreement. Maybe you are a lucky one, but in last few years they have been stricter.