Please be aware that Kuala Lumpur has multiple airports and that these results are for all airports serving the city.
The best month to fly between Kuala Lumpur and Hanoi is August and the most expensive month to fly is October. (Average prices, based on 241 datapoints.)
The best day to arrive at Kuala Lumpur is Wednesday and it would be best to avoid Thursday, as prices are on average 74.61% higher than on Wednesday. (Average prices, based on 241 datapoints.)