AIS sim. You will get it once you at the DMK or suvarnabhumi airport. used it solely for internet and whatsapp calls and it was a good deal. I paid 199 thb for 7 days. Network was superb.
It seems to me that you need to consult already in the city in which you are coming. The locals will be able to advise you on what is best for you. I can tell you that you are making the right choice to use WhatsApp. It really is a great application for communication. Especially if you install updates from Softgoza https://softgoza.com/
I don't know i don't travel Thailand i travel many country's like Austria Indonesia and 2 other thanks for the post amazing question... https://lulubox.cc/