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 May and the most expensive month to fly is March. (Average prices, based on 535 datapoints.)
The best day to arrive at Bangkok is Sunday and it would be best to avoid Tuesday, as prices are on average 31.12% higher than on Sunday. (Average prices, based on 535 datapoints.)
The best time to fly is at around 14. (Average prices, based on 819 datapoints.)