THE FOLLOWING INFO IS NOT SUITABLE FOR THE TYPICAL MONGERER WHO HAS NEVER TRAVEL SOLO BEFORE!
IF YOU CONSIDER YOURSELF STREET SMART AND "CRAZY" THEN PLEASE READ ON! 
I will post research material on this thread for the benefit of Special Forces and Cuntmando soldiers heading to all the shady cowboy border towns.
I'm not afraid of American Style Spenders going to such exotic places and destroy the market rate because they will not have the will and guts to explore those risky destinations.
Via China
Xishuangbanna Gasa Airport (JHG)
Kunming Changshui International Airport (KMG)
Nearest Airport to Mong La is Xishuangbanna Gasa Airport but the air ticket prices cost a bomb even if you fly from Guangzhou (CAN).
There will be stopovers if you are flying from outside of China using full service airlines.
Most economical way is still by AirAsia.
AirAsia has flights between:
Bangkok (DMK) to Kunming (KMG)
Kuala Lumpur (KUL) to Kunming (KMG)
Via Myanmar
Yangon (RGN) is damn far from Keng Tung (KET).
Air ticket prices also cost a bomb.
Average price S$500 for a return domestic flight.
*Disclaimer: Some busybody and cocky people claim my info and opinion are misleading as out of touch with Thailand. Please use info at your own discretion.