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 Medan is October and the most expensive month to fly is January. (Average prices, based on 614 datapoints.)
The best day to arrive at Bangkok is Thursday and it would be best to avoid Sunday, as prices are on average 25.85% higher than on Thursday. (Average prices, based on 598 datapoints.)