AirAsia will begin daily flights from Bangkok to Nakhon Phanom and the Sri Lankan city Colombo, starting on 15 February and 1 March, respectively.
The carrier started daily domestic Bangkok-Trang flights on 15 January.
Thai AirAsia chief executive, Tassapon Bijleveld, said: "We will continue to receive more brand-new Airbus A320 planes this year, which will enable us to introduce new routes and increase our destinations. At the moment, we are looking to explore China and other cities which are economic centres in the region."
According to the Innovata schedules, Nok Air operates flights from Bangkok Suvarnabhumi International to Nakhon Phanom and Trang airports. Cathay Pacific Airways, SriLankan Airlines and Thai Airways International operate Bangkok-Colombo flights, according to Innovata.