"...What about if you give somebody a gift, even if they are service staff, do you still not return the wai?.."
Well, I am guessing/speculating that if you are friends enough to give a gift then you have broken the status barrier and are accepting them as a peer. It is strange in that we don't have the same social status levels so it is not such a big deal for a farang to get it wrong, except the obvious silly cases. As Chanchao put it "wai everything that moves". LOL.
10

kevincorr
11

joyasia
Thanks Kevin, you guess right.
I think we do have social status levels that we show in different ways...eg, it would be considered rude when first meeting the mother of a friend or teacher, etc and call them by their first name, unless otherwise informed. A person in power, eg. a policeman would also demand a different degree of respect or familiarity. etc etc.
Joy
Pro tip