On a non O, you don't ever need to leave the country if you don't want to. While there are financial requirements, you don't have to provide any documents from a school or business when extending.
Anonymous participant it's good for 180 days at a time, over 5 years. At 180 days, you have to extend or go out of the country and come back in for a fresh 180.
As it stands now, if you extend in country, you basically have to meet the same requirements as your original application.
Leaving Thailand and coming back doesn't have the same level of scrutiny at this point.
if you're from the US, and you're doing a non O, you'll still have to deposit 800k for the first year in a Thai bank. In that first year, deposit 65k every month. In the 2nd year, you can do the income method.
There are some details, but that's the big picture.