Can you enter Thailand on a visa exempt at Don Muang Airport and obtain a 90-day stay?

@Miguel ************

if he gets 45 days then gets an extension will he get another 45 days or 30 days?

@Ronald ********

Entering on Tourist Visa or Visa Exempt, one of the requirements is to have proof of onward travel. Immigration doesn't often request this but they can, and if they are looking for a reason to deny entry to you, this is one of the reason they will use. But much more often your airline is the one that will enforce this. If you are going visa exempt then your airline will ask you to show proof of a ticket out of Thailand within 30 days. It doesn't matter if you plan on getting an extension, you will be stamped in for 30 days so you have to show proof of leaving Thailand within 30 days. Same with Tourist visa, but 60 days.

Will the airline always ask? No, but if they do ask and you can't show them proof, they will not let you board your flight and may demand you purchase a ticket right at that moment out of Thailand in order to board your flight.

To be clear, this is the airline enforcing Thai policies. Same as them asking to see your proof of vaccination or covid test.