Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 15:25 and arrives at Riyadh King Khaled International Airport at 18:55.
The flighttime is about 7h 30m. The distance travelled ("as the bird flies"): 5991 Km. So the average speed is roughly 799 Km.
There is an 4 hour time difference between Bangkok and Riyadh