Flight Don Mueang International Airport departs from Bangkok Don Mueang International Airport at 02:45 and arrives at Tokyo Narita International Airport at 12:55.The flight has a short stop at Kaohsiung.
The flighttime is about 8h 10m. The distance travelled ("as the bird flies"): 4524 Km. So the average speed is roughly 554 Km.
There is an 2 hour time difference between Bangkok and Tokyo