Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 22:30 and arrives at Tokyo Narita International Airport at 06:20.
The flighttime is about 5h 50m. The distance travelled ("as the bird flies"): 4511 Km. So the average speed is roughly 773 Km.
There is an 2 hour time difference between Bangkok and Tokyo
The best day to arrive at Bangkok is Saturday and it would be best to avoid Monday, as prices are on average 86.23% higher than on Saturday. (Average prices, based on 631094 datapoints.)
We have a lot more statistics for flights TG 640 and between Bangkok and Tokyo.
