This is great question, whether I am THAI, I think it's hard to explain. For those words, Thai people put it at the end of sentence depends on the situation as follows; - when you want to make your sentence more polite - "ja" "ka" "krub" is a nice word to say. - when they are closed enough - "wa" "woi" always use when you talk to your friend. - when you feel angry - "wa" and "woi" is sometime being used when you angry too. - when you want to complete the sentence - "la" "na" is some of the example for this. Btw, Thai people may compound 2 words to complete the sentence also such as, "na ja" "la ja" or anything else. Conclusion, it just the words to complete Thai sentence and the meaning of them depends on the time you want to use it.

Oh crap, i cant use enter to separate row???

This is great question, whether I am THAI, I think it's hard to explain. For those words, Thai people put it at the end of sentence depends on the situation as follows; - when you want to make your sentence more polite - "ja" "ka" "krub" is a nice word to say. - when they are closed enough - "wa" "woi" always use when you talk to your friend. - when you feel angry - "wa" and "woi" is sometime being used when you angry too. - when you want to complete the sentence - "la" "na" is some of the example for this. Btw, Thai people may compound 2 words to complete the sentence also such as, "na ja" "la ja" or anything else. Conclusion, it just the words to complete Thai sentence and the meaning of them depends on the time you want to use it.