Flight Changi Airport departs from Singapore Changi Airport at 10:50 and arrives at Seoul Gimpo International Airport at 18:35.
The flighttime is about 6h 45m. The distance travelled ("as the bird flies"): 2961 Km. So the average speed is roughly 439 Km.
There is an 1 hour time difference between Singapore and Seoul
The best day to arrive at Singapore is Monday and it would be best to avoid Saturday, as prices are on average 99.03% higher than on Monday. (Average prices, based on 407883 datapoints.)
We have a lot more statistics for flights KE 648 and between Singapore and Seoul.