@Amanda *******
The Multi Entry Tourist Visa is a "6-months validity visa".
You get a 60-days stay permit on each entry.
You need to do a border run to activate the next 60 days stay permit.
(You could apply for a 30 days extension for 1900.- THB, before doing the border run)
You can do unlimited entries within the visa validity.
If you exit and re-enter on the last day of the visa validity, you get a 60 days stay permit for the last time, taking you total stay to almost 8 months.
You can extend the last stay permit ONCE for 1900.- THB on Immigration, taking you to almost 9 months.
After that your chances for the rest of the year are naught, as Immigration won't allow any visa-exempt entries consecutively after you have exhausted your touristic stay permits
Alternatively, you can buy the 5 year ELITE Visa, which will allow you 5 years of uninterrupted stay, for 900,000.- THB