Flight Changi Airport departs from Singapore Changi Airport at 22:30 and arrives at Seoul Incheon International Airport at 05:45.
The flighttime is about 6h 15m. The distance travelled ("as the bird flies"): 2923 Km. So the average speed is roughly 468 Km.
There is an 1 hour time difference between Singapore and Seoul
The best day to arrive at Singapore is Tuesday and it would be best to avoid Friday, as prices are on average 43.11% higher than on Tuesday. (Average prices, based on 663788 datapoints.)
We have a lot more statistics for flights KE 644 and between Singapore and Seoul.