Please be aware that Bangkok has multiple airports and that these results are for all airports serving the city.
The best month to fly between Bangkok and Hat Yai is June and the most expensive month to fly is May. (Average prices, based on 278 datapoints.)
The best day to arrive at Bangkok is Sunday and it would be best to avoid Thursday, as prices are on average 74.64% higher than on Sunday. (Average prices, based on 267 datapoints.)
The cheapest airline flying from Bangkok to Hat Yai is Thai AirAsia. They are 40% cheaper than Thai Airways. (Average prices, based on 286 datapoints.)