@Vanessa *********
When you arrive without a visa, you will receive a 60-days stay permit. It is called "visa-exempt entry"
This 60-days stay permit can be extended on Immigration for 1900.- THB for 30 more days.
At the moment it is TOTALLY unclear, how many times in a row you can make a border bounce and receive another 60-days stay permit.
Some say you can do it unlimited times, and others say that you can only stay in Thailand without a visa for a maximum of 90 days within a 180-days period. Time will show who is right.
So, as long as it has not been confirmed, you should use a safe option.
If you want to play 100% safe, apply for a 60-days single entry tourist visa in your home country, enter Thailand, get stamped in on this visa for 60 days. Extend on Immigration for 30 more days.
Before the stay permit expires, do a “border run”. Exit Thailand and re-enter visa-exempt. You will get stamped in for 60 days. And these 60 days stay permit can get extended for 30 more days.
60+30 and 60+30 = 180 days theoretical stay permit