Usage of "How can I help you?"

[Storm]

Which one is the most polite....

1. How may I help you?
2. How can I help you?

And can the sentence "Is there anthing I can do for you?" be shorten to "Anything I can do for you?" in spoken situations?

The Thais always use this in a short phrase, how can I teach them only if this is wrong?

[Mister Micawber]

.
Those are all OK. 'Can' and 'Anything...' are less formal.
.
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Native English teacher at Mister Micawber's