Hey my daughter won and she is NOT in a hi so school! Of course she is luk krung so kind of cheating!

I don't understand how it's cheating.

Being Leuk Kreung isn't even really an unfair advantage, as it's not a competition of purely their English ability. Instead it's about their acting ability and the English itself is from a script, so their ability to put together grammatically correct sentences and access to a large vocabulary isn't that important, the only real advantage they have is that their pronunciation might be a bit better (But admittedly, with the judging panel usually consisting of more Thai than foreign teachers, a Thai accent might be a bonus).

For competitions like an impromptu speech, it'd be a little bit unfair to put leuk kreung in with the regular Thai students. Although to be fair, it's going to be a competition based on their ability to create a speech/opinion/argument within a short space of time, and this does level the playing field a bit (Although leuk kreung, as NES, would still definitely have an advantage over their Thai counterparts. Particularly as they'd likely have assistance from their parents, as opposed to just their Thai teachers (Who often confuse the concept of what an "impromptu" speech entails).