Thanks very much for the detailed reply.

Wow. I had absolutely no idea I'd actually asked a question that had such a complex answer.
As far as "Srey" is concerned, you say it is, by one definition, "to be female". Does this equate with the any of the western equivalents, such as Miss, Mrs, Mademoiselle, Fraulein etc? Similarly, does "Pros" translate to Mr, Herr, Monsieur etc? Or is that incorrectly assigning a western linguistic or social construct that simply doesn't apply in Khmer language and society?
As far as the "a-" prefix is concerned, I've only ever used it with people I been introduced to by name that starts with "a-". My puzzlement about its use didn't get prompted by the presence of the "a-", it was its absence. I've just noticed a typo in my original post that may have reduced the clarity of what I was saying.
At first, I though there was a lot of names beginning with "A" and that the dropping of the "A" was just a shortening of the name. For example, I was introduced to someone called Aliu (sp?). Her friend told me that was her name but when I later met her barang boyfriend he referred to his girlfriend Liu, never once using the "A-". I figured that it was just a shortening of her name. I heard other Khmers doing something similar, Aporn being called Porn, Alin being called Lin etc.
Then one day the flicker of a light went on in my head - and I don't know what caused it or when it happened - that made me think, "Hold on. That guy's girlfriend isn't birth named Alin, she was being called A-Lin. What's that about? What does that mean?"
I assume that the usage I encountered was the, " It is commonly used in addressing close friends...when preceding the name of a girl, it conveys a notion of endearment" area of definition because it was people introducing friends to me using that appellation for them.
I suppose it's not beyond possibility that there was a subtle social message that went way over my head if the user was actually implying they were "persons regarded as inferiors" because they didn't actually like them that much.
