My memory is shaky...I think you can stay for a month, then get extentions when you get to know the locals that know what they are doing...Expats, locals...They can help out with all that...
The rules have changed this month without any notice given.
Now, you can maybe do one visa run then after that have to leave Thailand for a few days and apply for a tourist visa at a Thai embassy. Its for 60 or 90 days and I think can be renewed for a further 15 or 30 days in Thailand.
I've read if cases of people doing the visa run and refused reentry by officials.
So it's gotten more complicated now. Before, it was possible (depending on passport) to do a visa run every 15 or 30 days by land or always 30 days by air.
One of the reasons why this has gone through is probably because there is no properly functioning government at the moment and every government agency is just doing their own thing.