Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 17:25 and arrives at Koh Samui Samui International Airport at 18:30.
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 Wednesday and it would be best to avoid Sunday, as prices are on average 20.58% higher than on Wednesday. (Average prices, based on 4869914 datapoints.)
This graph shows the distribution of prices found in the past years for this flight. (Average prices, based on 165 datapoints.)
We have a lot more statistics for flights PG 181 and between Bangkok and Koh Samui.