Flight Phuket International Airport departs from Phuket Phuket International Airport at 14:55 and arrives at Singapore Changi Airport at 17:40.
The flighttime is about 1h 45m. The distance travelled ("as the bird flies"): 646 Km. So the average speed is roughly 369 Km.
There is an 1 hour time difference between Phuket and Singapore