How to say 'when' in thai language?

I've struggled with this a bit as when is used so often in English and with different meanings, and it can't always be translated as 'meua-rai'. From what I gathered in the past tense it's 'meua' เมี่อ, as in a sentence like 'when I was ten years old....'. In situations where you could swap whenever for when and still have the sentence make sense, you can use 'waylah tee', like 'I am happy when I see you' สุขใจเวลาที่เจอกับเธอ

- Mike