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 April and the most expensive month to fly is May. (Average prices, based on 372 datapoints.)
The best day to arrive at Seoul is Wednesday and it would be best to avoid Tuesday, as prices are on average 25.42% higher than on Wednesday. (Average prices, based on 263 datapoints.)
The cheapest airline flying from Seoul to Hong Kong is Jeju Air. They are 49% cheaper than Cathay Pacific. (Average prices, based on 378 datapoints.)
The best time to fly is at around 22. (Average prices, based on 579 datapoints.)