Commercial flights have been developed in past recent years in South-East Asian countries. Taking flight from Chiang Mai, Thailand to Phnom Penh, Cambodia, is getting easier.
Chiang Mai to Cambodia:

Tomorrow in the wee hours of the morning Christy and I will be catching a flight to Phnom Phen, Cambodia. A country still trying to emerge from it’s history of war and political unrest. A county where in the late 1970′s Pol Pot was the leader and ordered the killing of more then a million of his own people. A country that doesn’t have a single ATM in the entire place. Cambodia will be a challenge for us but I know the chellenge will be worth it to see a land that is still largely untouched.