Flight Hong Kong International Airport departs from Hong Kong Hong Kong International Airport at 08:35 and arrives at Phnom Penh Phnom Penh International Airport at 10:15.
The flighttime is about 2h 40m. The distance travelled ("as the bird flies"): 1080 Km. So the average speed is roughly 405 Km.
There is an 1 hour time difference between Hong Kong and Phnom Penh