Please be aware that Seoul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Seoul and Singapore is February and the most expensive month to fly is May. (Average prices, based on 271 datapoints.)
The best day to arrive at Seoul is Wednesday and it would be best to avoid Sunday, as prices are on average 85.95% higher than on Wednesday. (Average prices, based on 226 datapoints.)
The cheapest airline flying from Seoul to Singapore is Scoot-Tiger. They are 65% cheaper than Korean Air. (Average prices, based on 282 datapoints.)
The best time to fly is at around 15. (Average prices, based on 542 datapoints.)