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 January. (Average prices, based on 2196 datapoints.)
The best day to arrive at Seoul is Sunday and it would be best to avoid Monday, as prices are on average 26.72% higher than on Sunday. (Average prices, based on 2135 datapoints.)
The cheapest airline flying from Seoul to Hong Kong is Hong Kong Express. They are 53% cheaper than Cathay Pacific. (Average prices, based on 2207 datapoints.)
The best time to fly is at around 22. (Average prices, based on 3555 datapoints.)