1. ปัญหา - problem. Glad this word exists in Thai. In Chinese, the word for 'question' and 'problem' are actually the same. It's 問題. So... although I suppose a native speaker gathers from context what the correct meaning is, asking a student if he has any 問題 regarding the information we just studied still seems vague to me. Asking if you have any questions is one thing, but asking if there's a problem is different. If talking specifically about a problem, as in hardship, you could use 難題, which is literally more like 'difficulty' and this serves to be more clear, but it's also more serious. Also, simply asking someone with a blank look on their face if they have a question is far more polite (and probably more well-received) than asking that same blanked out person if they have a problem; but again, I suppose this distinction just isn't... as paid attention to as in English. Glad it's different in Thai.
2. คอย - to wait. (this is also part of the word for 'watch tower' (or one of them, anyway). It's หอคอย, but for the one we use in service, it's หอสังเกตการณ์. Yeah. Longer. The former actually means 'waiting tower' whereas the latter one is a tower for watching, but they're both translated as watchtower. I can see why the latter is more appropriate.