Flight Changi Airport departs from Singapore Changi Airport at 08:40 and arrives at Siem Reap Siem Reap-Angkor International Airport at 09:45.
The flighttime is about 2h 05m. The distance travelled ("as the bird flies"): 322 Km. So the average speed is roughly 155 Km.
There is an 1 hour time difference between Singapore and Siem Reap