Flight Incheon International Airport departs from Seoul Incheon International Airport at 23:15 and arrives at Singapore Changi Airport at 04:55.
The flighttime is about 6h 40m. The distance travelled ("as the bird flies"): 2923 Km. So the average speed is roughly 438 Km.
There is an 1 hour time difference between Seoul and Singapore
The best day to arrive at Seoul is Friday and it would be best to avoid Monday, as prices are on average 570.46% higher than on Friday. (Average prices, based on 691563 datapoints.)
We have a lot more statistics for flights VA 5675 and between Seoul and Singapore.