Because foreigners can be good too, many start young (started at 13 myself, not as young as some but younger that alot of others). Forigners records can be deceiving because of the amature scene, guys may appear to be less experienced than they really are because of this, a guy with a pro record of 35-3 for example may also have 200 amateur fights that are obviously not on this record and thus unknown to most people watching him fight as a pro. Whereas in thailand this works to the opposite effect, a 15 year old may have 100 fights on his pro record because of the lack of amateur scene but 30 or 40 of those fights could probably be considered amature level in terms of skill. Although I've never fought a thai myself I know guys who have and have spoken to plenty others, alot of guys say they fight more of a kickboxing style against thais, light on the feet, lots of pressure and angles and movement, the Thais are experts at this sport obviously, so fighting in a thai style against a master of the thai style probably isn't going to get you a win