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 Phnom Penh is February and the most expensive month to fly is August. (Average prices, based on 1472 datapoints.)
The best day to arrive at Kuala Lumpur is Saturday and it would be best to avoid Sunday, as prices are on average 86.76% higher than on Saturday. (Average prices, based on 1416 datapoints.)