Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 18:30 and arrives at Vientiane Wattay International Airport at 19:45.
The flighttime is about 1h 15m. The distance travelled ("as the bird flies"): 223 Km. So the average speed is roughly 178 Km.
The best day to arrive at Bangkok is Monday and it would be best to avoid Tuesday, as prices are on average 134.62% higher than on Monday. (Average prices, based on 361845 datapoints.)
We have a lot more statistics for flights TG 574 and between Bangkok and Vientiane.
