Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 19:35 and arrives at Koh Samui Samui International Airport at 20:45.
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 Friday and it would be best to avoid Sunday, as prices are on average 152.33% higher than on Friday. (Average prices, based on 5038214 datapoints.)
We have a lot more statistics for flights PG 191 and between Bangkok and Koh Samui.
