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 Hong Kong is March and the most expensive month to fly is April. (Average prices, based on 550 datapoints.)
The best day to arrive at Seoul is Wednesday and it would be best to avoid Monday, as prices are on average 45.04% higher than on Wednesday. (Average prices, based on 610 datapoints.)
The cheapest airline flying from Seoul to Hong Kong is Jin Air. They are 66% cheaper than Cathay Pacific. (Average prices, based on 569 datapoints.)
The best time to fly is at around 21. (Average prices, based on 993 datapoints.)