Please be aware that Bangkok and Tokyo has multiple airports and that these results are for all airports serving the city.
The best month to fly between Bangkok and Tokyo is September and the most expensive month to fly is April. (Average prices, based on 665 datapoints.)
The best day to arrive at Bangkok is Sunday and it would be best to avoid Tuesday, as prices are on average 34.69% higher than on Sunday. (Average prices, based on 1556 datapoints.)
The cheapest airline flying from Bangkok to Tokyo is Thai Airways. They are 29% cheaper than All Nippon Airways. (Average prices, based on 673 datapoints.)
The best time to fly is at around 2. (Average prices, based on 988 datapoints.)
SGD
