Flight Suvarnabhumi Airport departs from Bangkok Suvarnabhumi Airport at 17:15 and arrives at Jakarta Soekarno–Hatta International Airport at 20:55.
The flighttime is about 3h 40m. The distance travelled ("as the bird flies"): 830 Km. So the average speed is roughly 226 Km.
The best day to arrive at Bangkok is Sunday and it would be best to avoid Wednesday, as prices are on average 312.15% higher than on Sunday. (Average prices, based on 13156951 datapoints.)
We have a lot more statistics for flights NH 869 and between Bangkok and Jakarta.