Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 09:15 and arrives at Koh Samui Samui International Airport at 10:45.
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 Monday and it would be best to avoid Saturday, as prices are on average 75.32% higher than on Monday. (Average prices, based on 5454873 datapoints.)
We have a lot more statistics for flights PG 115 and between Bangkok and Koh Samui.
