At age 15 you are allowed to fly alone with your parents purchasing the ticket; our daughter flew solo her first time from San Francisco to Manila when she was 12 years old. Actually she was upgraded to first class because there was an elderly Filipina in First Class who didn't speak much English ( very rare ) so was helped translate communication between her and the flight attendents. She LOVED service, menu choices and extra comfort and almost regretted arriving in Manila.
At 15 years old you could travel around most countries in Asia without a problem but then again you always must be extra careful when traveling in the lands of the "Ten Million" laws restricting almost all human behavior. It's probably a good idea to follow the tips mentioned above.
An English friend of mine, Nick from one of those old families was treated by his grandfather for his 16th birthday a flight and 2 week trip to Bangkok to "sew his wild oats" so to speak; ahhh what a trip, being "on the road" at 15 year old, you're a LUCKY soul. Hope you made the trip and had