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 Hanoi is October and the most expensive month to fly is August. (Average prices, based on 312 datapoints.)
The best day to arrive at Bangkok is Thursday and it would be best to avoid Wednesday, as prices are on average 100.56% higher than on Thursday. (Average prices, based on 312 datapoints.)
The cheapest airline flying from Bangkok to Hanoi is VietJet Air. They are 34% cheaper than Thai Airways. (Average prices, based on 319 datapoints.)
The best time to fly is at around 6. (Average prices, based on 598 datapoints.)