Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 08:00 and arrives at Chiang Mai Chiang Mai International Airport at 09:20.
The flighttime is about 1h 20m. The distance travelled ("as the bird flies"): 221 Km. So the average speed is roughly 166 Km.
The best day to arrive at Bangkok is Sunday and it would be best to avoid Monday, as prices are on average 254.5% higher than on Sunday. (Average prices, based on 13615848 datapoints.)
We have a lot more statistics for flights WY 5866 and between Bangkok and Chiang Mai.