Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 10:10 and arrives at Koh Samui Samui International Airport at 11:40.
The flighttime is about 1h 30m. The distance travelled ("as the bird flies"): 113 Km. So the average speed is roughly 75 Km.
The best day to arrive at Bangkok is Saturday and it would be best to avoid Friday, as prices are on average 93.98% higher than on Saturday. (Average prices, based on 5540298 datapoints.)
We have a lot more statistics for flights PG 127 and between Bangkok and Koh Samui.
