Take ‘mai pann rai’.

Is it true that the phrase has different meanings depending on context?

Near as I can tell it can mean:
* “You are welcome.” after thanking someone for a good deed.
* “No problem.” to defuse a situation that may become heated.

I find its really easy to equate it with english “No worries, not a problem.” true?

And as usual always best to add “khrab” at the end to be polite?

Not that any situations have become heated, except when me being a stupid aussie who is used to pay as you go drinking walked out for a smoke an left his checkbin on the table. Only had to do it once to learn the lesson.