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 Chiang Rai is May and the most expensive month to fly is November. (Average prices, based on 1751 datapoints.)
The best day to arrive at Bangkok is Wednesday and it would be best to avoid Friday, as prices are on average 61.49% higher than on Wednesday. (Average prices, based on 915 datapoints.)
The cheapest airline flying from Bangkok to Chiang Rai is Thai Vietjet Air. They are 11% cheaper than Thai AirAsia. (Average prices, based on 1762 datapoints.)