Questions about Thailand

I really liked this movie, the way they portrayed it in such an innocent way and pure kind of love between two teenage girls, it really makes you say: awww that's so cute!
But I did feel somehow puzzled, at first I couldn't say whether if it was an elite private high school, a technical college or an university.. I mean from my [western perhaps?] point of view the girls and boys seemed all too childish, both in looks and attitudes, are Thai university undergraduates all like that?

I don't know if it was intentionally a thing of the producers or if it is accurate for Thai society. For instance, Kim's fears of darkness, thunders & bugs and her awkward reactions; Pie's way of treating Kim, which instead of being more anti-'tom' prejudice, seemed more like a non-sensical childish tantrum; Jane, P'in, the nerd girl, etc, they all had attitudes that match more 14 or 15 year-olds instead of 18~19yo... Did I miss something here? Would a Thai please enlighten my perhaps blindfolded view?

I mean it would make more sense for me if this happened when they were just entering high school, but then again of course it would be even more prejudiced for parents and all.

Other than that, I loved the movie, would recommend it a 100%