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 Mumbai is April and the most expensive month to fly is September. (Average prices, based on 475 datapoints.)
The best day to arrive at Bangkok is Thursday and it would be best to avoid Sunday, as prices are on average 39.06% higher than on Thursday. (Average prices, based on 423 datapoints.)