What are the official rules for US citizens regarding the number of entries into Thailand without a visa?

(US Citizen) Are there official rules on the number of times you can enter without a visa? I was here in December last year and extended into January. I left for nearly 4 months and just came back. Border patrol had a lot of questions this time. Feeling lucky to have got in. Not sure if I am pushing the boundaries of entering without a visa. I will stay 28 days this time and was planning on coming back in December. So that would be 3 entries with one extension and one entry was in the previous year.

Also what happens if you are denied entry will I be able to just quickly book a flight and fly out a few hours later or will I need to sit in some detention center?

Should add I make money from US real estate investments and am a shareholder in a Nevada company. So very easy to prove I do not work here. And I never enter or exit by land.