Flight Changi Airport departs from Singapore Changi Airport at 01:10 and arrives at Seoul Gimpo International Airport at 08:35.
The flighttime is about 6h 25m. The distance travelled ("as the bird flies"): 2961 Km. So the average speed is roughly 461 Km.
There is an 1 hour time difference between Singapore and Seoul
The best day to arrive at Singapore is Sunday and it would be best to avoid Saturday, as prices are on average 138.16% higher than on Sunday. (Average prices, based on 400558 datapoints.)
We have a lot more statistics for flights KE 646 and between Singapore and Seoul.