What are the best visa options for traveling and staying longer in Thailand while being visa exempt?

Visa exempt will give you 30, + one additional 30 days extension for a total of 60. Immigration has been know to decline entry if they feel that people are abusing visa exempt so something to keep in mind if you plan on bouncing around.

The Tourist Visa, TR60 or Single Entry Tourist Visa, will give you 60, + one additional 30 days extension for a total of 90. Easy to apply for online, usually takes a week.

The STV, Special Tourist Visa, gives 90 days, + two 90 day extensions. No idea how long it takes to get but have read the process is cumbersome.

If the covid covid extension is available after January 25 you can get an additional 60 days. The IO's usually require you have used all extensions on your original entry prior to allowing this... varies per office. If it's extended, entering on a visa exempt would be better since you can apply for before potentially expires.

If you don't like the uncertainty of that, TR60 is the way to go.

Currently, land borders are closed but you can fly. Cambodia is open but need a visa, PCR, negative ATK on arrival and if vaxxed can travel around. You can get a new TR60 from the Thai Embassy to re- enter but would need to meet all the other requirements. Laos has limited opening for tour groups and I think Vietnam is similar.

Not a good time to go in and out.if your tested positive after your first quarintine you will go back in for the second round.

Are you from USA?

Each time you enter Thailand you need to apply for the Thailand pass. It's just like the passenger locator forms other countries require. There is not a lot of opportunities for travel between countries in the region, still a lot of restrictions. You would need to research their entry requirements thoroughly.