เกรงใจ has no English word. เกรง is to be in awe of, or to fear; ใจ is heart. Together: the reluctance to impose on someone, to be a burden, to make another person go to trouble on your behalf.
It is not shyness and it is not politeness. It is a live social force, and once you can see it, a great deal of otherwise baffling behaviour becomes legible.
- เกรงใจkreːŋ.tɕaj
to be reluctant to impose
- เกรงkreːŋ
to fear, to be in awe of
- ใจtɕaj
heart, mind
What it looks like
Your neighbour will not ask you for a lift even when you have offered twice. A colleague will say the food is fine when it is cold. Someone will decline the first offer of anything, and mean yes.
It also runs the other way, and this is the part that matters for you: a Thai person who thinks you are going to too much trouble may quietly stop asking you things at all, including whether you understood.
How to use it
Offer more than once, and make the offer small enough to accept. 'I am going that way anyway' removes the debt, and removing the debt is the whole trick.
And when someone does something for you, ไม่เป็นไร is not only 'never mind'. Used in reply it says 'no debt has been created here', which is exactly what the other person is worrying about.
- ไม่เป็นไรmâj.pen.raj
never mind; it's nothing; you're welcome
the most useful three syllables in Thai