Mysterious sign in Sheung Shui Wai

I had some time to kill earlier this week so I decided to finally explore some parts of Hong Kong I'd never seen. I headed up to Sheung Shui where I wandered around the old market town of Shek Wu Hui as well as Sheung Shui Wai, a large village to the north.

While in Sheung Shui Wai I came across this odd sign which was placed near an obscure entrance to the village. I was intrigued because the last line seems to be in Vietnamese. The gist of it seems to be "keep out, this is for Sheung Shui Wai people only." But can anyone explain the context and significance of this sign?

The locals are just going territorial.............

Hi there,
There are still some local villages that had been and still is very territorial. They don't like strangers and might chase strangers out of their villages. As for the line in Vietnamese I really no idea. I could not recall any Vietnamese refugee camps near Sheung Shui back then.

Best Regards,