like this?

https://www.sinchew.com.my/?p=6985866

nanti i sendiri yg kena, how?

what is that? although I have googled but cant understand. Please ellaborate more? 

Just as he said, this was done just two weeks ago on cambodia vs thailand border.

Since those people active at night, why not just put some hidden speaker then have sudden girl crying or laughing burst ... but then again gonna be kinda careful cause if someone die of a heart attack on your property its gonna be even more troublesome.

All in all at serious note you should consult a lawyer and see what are your legal option first and what are the punishment for traspassers. Cause there are consequences ...... the higher your security is the more dangerous type of criminal you will encounter. And the hardest thing to control is vase land ownership, cause people will act ignorant and push the limit of what they can get away with.