In Thai tradition, a Kuman Thong is an unborn fetus that is given an incantation to bring about a demonic possession of the body of the fetus, and then gold leaf is used to trap the being in the body, thus giving the owner dominion over the entity from there on out, or something to that effect.
Maybe gold is used as some "container" for evil spirits that these people believe they're channeling while they're diddling kids and drinking their blood?
Yeah, there was some dude caught crossing a border with a briefcase full of these little bastards a few years back. I'm sure it was connected with the other bad actors we know are conducting business in Thailand and Cambodia.
Also, further reading into ancient Egyptian practices related to the Pharaoh coating his skin in gold, and their burial practices would probably be a good related dig. I wouldn't know where to look for the nuances of ancient Egyptian burial rituals though haha. I'm more of a big-picture autist rather than a granular one.