This is your quickest option, but obviously also the most expensive one. Both AirAsia and Thai Airways have regular flight services from Bangkok to Khon Kaen. Flights depart from Bangkok’s Don Muang Airport and arrive 50 minutes later on Khon Kaen Airport, just west of the city off Highway 12. Regular flight tickets cost between 2,000 to 3,000 THB, however there are some good promotions from time to time at AirAsia with fares from as low as 1,200 THB.