Can anyone confirm whether or not a Thai citizen requires a passport for domestic airline travel?

When I took a girl to Chiang Mai her Thai ID card was all she used.

No passport required...................but good to have for check-in

Photo ID should be ok

No, they don't need a passport and neither do foreigners. For Thais their photo ID should be fine. Whenever I travel domestically I leave the passport home (bring a copy) and just use my Thai driver's license for check in. Never even had a second thought from the workers.

No, they don't need a passport and neither do foreigners. For Thais their photo ID should be fine. Whenever I travel domestically I leave the passport home (bring a copy) and just use my Thai driver's license for check in. Never even had a second thought from the workers.

Im the same, only ever take a copy and my origional thai driving license, I have never had a problem yet. In answer to the OP my wife just uses her I.D card when flying internally.

A lot of Thai people do not have passports but are supposed to carry their ID card at all times so that is fine for domestic air travel or checking into hotels, and even crossing the border into Laos if they so desire.

Foreigners are supposed to carry their passports at all times, though like many I carry a copy with me and leave it at home. I prefer tho carry it with me when flying and certainly when checking into a hotel, hoteliers are obliged to notify Immigration of foreigners staying in their hotel, so I feel safer carrying it with me.