How many times can I enter Thailand in a year on a 30-day entry at the airport?

There is no official limit on the number of times you can enter Thailand on a 30-day visa waiver by air. However, if you frequently enter Thailand, immigration may question your status as a genuine tourist. Some commenters noted that repeated entries (especially more than three times) could raise flags and result in entry denial. Entering by land typically has a limit of two entries per calendar year.