Hi Derrick "Noi jai" means to feel hurt or slighted. For example, when your friends forget your birthday, it makes you feel a bit disappointed for what you hope or expect. Or if mother gives a toy yo only one of her children, the other one will feel Noijai because he's got nothing. As for "Khor thood", you say this when you do something bad to another person or you regret something and you want to say sorry for that, like when you step on someone's foot. have fun with thai language :)