Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 15:15 and arrives at Koh Samui Samui International Airport at 16:25.
The flighttime is about 1h 10m. The distance travelled ("as the bird flies"): 113 Km. So the average speed is roughly 97 Km.
The best day to arrive at Bangkok is Tuesday and it would be best to avoid Sunday, as prices are on average 88.55% higher than on Tuesday. (Average prices, based on 5040180 datapoints.)
We have a lot more statistics for flights PG 161 and between Bangkok and Koh Samui.