In Malaysia it is proper to call older people Uncle and Aunty. This is because age is hugely important in Asia. The older you are, the more respect you're entitled to.
I'm 44 now so I'm beginning to get quite a bit of it. As I'm half Dutch and half Scots, this doesn't sit easily with me. I'm extremely informal plus my automatic reaction is, we're not related, so why call me that?
Luckily Malaysians are a pretty easy going bunch and there are some alternatives.
For example, the first time I went to our local wet market and Chinese vegetable girl greeted me with a, "Hello Aunty! Whatcha want?" I gave her a steely look and said, "Aunty?!" in mock outraged tones.
She gave me a thoughtful stare back and said, "How about Sister?" Now that I can live with because ah moi means sister in Hakka and Cantonese. It can also be used in the sense of hey-babe-how's-it-hanging but that's another story....
The best one for getting around the Aunty/Uncle/respectful title thing is the Malay vegetable lady. She just calls everyone Darling. "Hello, darling? What do you want, darling? See you later, darling!" This is her stall, and she's the lady on the left.
I'm kind of extra glad for darling vegetable lady's idiosyncrasy because the equivalent of ah moi or aunty in Malay is kak meaning older sister. But as kak in Dutch means shit, I just can't warm up to that expression.