Flight Changi Airport departs from Singapore Changi Airport at 02:25 and arrives at Seoul Gimpo International Airport at 09:50.
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 Thursday and it would be best to avoid Sunday, as prices are on average 82.15% higher than on Thursday. (Average prices, based on 402266 datapoints.)
We have a lot more statistics for flights SQ 612 and between Singapore and Seoul.