Flight Changi Airport departs from Singapore Changi Airport at 08:30 and arrives at Semarang Achmad Yani International Airport at 09:40.
The flighttime is about 2h 10m. The distance travelled ("as the bird flies"): 760 Km. So the average speed is roughly 351 Km.
There is an 1 hour time difference between Singapore and Semarang