crazysally
Hello, I've been using GOS in Thailand for over a year now.
The best way to get a sim card and not be charged a 7-11 or Mom & Pop Store Premium is to go to a TRUE, DTAC, or AIS shop. They're in most of the major malls and superstores such as BIG C or Tesco's all over the country.
Ask them for a prepaid sim promotion, its usually starts with something like 30gb for 200thb a month or 50gb for 250 - 300thb a month. 7-11 would charge you the same price for a week's data.
You could even ask these service providers (personally I use TRUE), to hook you up with an eSim after choosing a promotion.