Flight Phuket International Airport departs from Phuket Phuket International Airport at 20:10 and arrives at Singapore Changi Airport at 23:15.
The flighttime is about 2h 05m. The distance travelled ("as the bird flies"): 646 Km. So the average speed is roughly 310 Km.
There is an 1 hour time difference between Phuket and Singapore