I've been travelling on visa exempt for 13 years and some years in Thailand 7 times in one year and minimum 3 times in one year with no problems. I'll be going again in March and was there January and February this year also with no issues
60 days on every entry irrelevant of what country you arrive from. Although land crossings may have restrictions. Last I heard was only 2 x land crossing per calender year. Don't quote me on that