Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 17:55 and arrives at Koh Samui Samui International Airport at 19:00.
The flighttime is about 1h 05m. The distance travelled ("as the bird flies"): 113 Km. So the average speed is roughly 104 Km.
The best day to arrive at Bangkok is Sunday and it would be best to avoid Friday, as prices are on average 134.61% higher than on Sunday. (Average prices, based on 5450102 datapoints.)
We have a lot more statistics for flights PG 177 and between Bangkok and Koh Samui.
