Flight Kansai International Airport departs from Osaka Kansai International Airport at 23:55 and arrives at Bangkok Don Mueang International Airport at 03:50.
The flighttime is about 5h 55m. The distance travelled ("as the bird flies"): 3943 Km. So the average speed is roughly 666 Km.
There is an 2 hour time difference between Osaka and Bangkok