Flight Hong Kong International Airport departs from Hong Kong Hong Kong International Airport at 01:40 and arrives at Singapore Changi Airport at 05:30.
The flighttime is about 3h 50m. The distance travelled ("as the bird flies"): 1322 Km. So the average speed is roughly 345 Km.
The best day to arrive at Hong Kong is Saturday and it would be best to avoid Sunday, as prices are on average 101.31% higher than on Saturday. (Average prices, based on 2003420 datapoints.)
We have a lot more statistics for flights CX 659 and between Hong Kong and Singapore.