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 Penang is May and the most expensive month to fly is April. (Average prices, based on 514 datapoints.)
The best day to arrive at Bangkok is Monday and it would be best to avoid Friday, as prices are on average 33.06% higher than on Monday. (Average prices, based on 481 datapoints.)