I was watching this video from a Thai-Australian actor, who was raised in the later country and only moved to Thailand when he was 20. Apparently growing up, his mom tried to teach him Thai, but he was having none of it at the time.
Then, he moved to Thailand and had to learn Thai well enough to be able to act in that language. He said that with Thai, the same word can mean differing things depending on the inflection of your voice. So it can sound like you're saying the same word, but still be saying it the wrong way.
I guess every language has its own insane quirks.