A report on Monday said hundreds of passengers on Nok Air were left stranded overnight in Bangkok after a pilot strike.
The International Air Transport Association, IATA, said the flights were cancelled because Nok Air was in the process of upgrading its standards to meet with IATA Operation Safety Audit standards.
Nok Air is the third-largest budget airline in Thailand.
It said this had become imperative because some pilots did not meet the new criteria and went on strike to express their discontent.
The chief executive of Nok Air, Patee Sarasin, said the airline was negotiating with the pilots and trying to find alternative airlines for stranded passengers.
Thailand-based airlines have come under criticism after the country’s civil aviation authority was downgraded by a UN body last year for regulatory oversights.