Flight Changi Airport departs from Singapore Changi Airport at 04:15 and arrives at Kolkata Netaji Subhas Chandra Bose International Airport at 05:55.
The flighttime is about 4h 10m. The distance travelled ("as the bird flies"): 1717 Km. So the average speed is roughly 412 Km.
There is an 2.5 hour time difference between Singapore and Kolkata