A late-evening fire grounded all flights and stranded hundreds of passengers at Ubon Ratchathani International Airport on Tuesday.
No casualties were reported, but it was unclear early Wednesday when flights would resume.
Reports from the airport said a short circuit in a runway light's control panel caught fire at around 8pm.
Thai Airways International, AirAsia and Nok Air all cancelled flights to and from Ubon Ratchathani until further notice.
Airlines offered stranded passengers a ride back to the province capital by bus, but many reportedly chose to camp out at the airport.
Passenger Laddawan Mongkol, 62, scheduled to fly to Bangkok for a medical appointment on Wednesday, told Thai Rath newspaper that Nok Air staff told her they expected an update at 11am.