Flight Samui International Airport departs from Koh Samui Samui International Airport at 21:00 and arrives at Bangkok Suvarnabhumi Airport at 22:30.
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 Koh Samui is Saturday and it would be best to avoid Sunday, as prices are on average 12.7% higher than on Saturday. (Average prices, based on 1615622 datapoints.)
We have a lot more statistics for flights PG 192 and between Koh Samui and Bangkok.
