Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 19:15 and arrives at Chiang Mai Chiang Mai International Airport at 20:30.
The flighttime is about 1h 15m. The distance travelled ("as the bird flies"): 221 Km. So the average speed is roughly 177 Km.
The best day to arrive at Bangkok is Tuesday and it would be best to avoid Friday, as prices are on average 61.07% higher than on Tuesday. (Average prices, based on 8639252 datapoints.)
We have a lot more statistics for flights TG 120 and between Bangkok and Chiang Mai.