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 546 datapoints.)
The best day to arrive at Seoul is Sunday and it would be best to avoid Monday, as prices are on average 50.66% higher than on Sunday. (Average prices, based on 546 datapoints.)
The cheapest airline flying from Seoul to Hong Kong is Jin Air. They are 66% cheaper than Cathay Pacific. (Average prices, based on 564 datapoints.)
The best time to fly is at around 21. (Average prices, based on 892 datapoints.)