well I’ve been several times with either visa exempt or a 60 day visa always staying for 90 days and always having a return ticked for the full period flying either Qatar or Finair, never a problem , maybe I was just lucky.
like you say depends where he is, I was in Jontiem , 5 hours in the sun, agent charged 4000 baht which includes the 1900 visa , so cost me 2100 to spend 5 hours by the pool instead of in a queue 😊😊