Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 12:20 and arrives at Osaka Kansai International Airport at 20:05.
The flighttime is about 5h 45m. The distance travelled ("as the bird flies"): 3931 Km. So the average speed is roughly 684 Km.
There is an 2 hour time difference between Bangkok and Osaka