Thanks Aaron! If folks with little understanding of SEA culture can vibe with it, that is like... oooof... dream outcome. :D So fingers all crossed for that!
These are not TTRPG books and also not fictional(in a way) but are completely fascinating books on Malay supernatural, written by British administrators decades ago. They are a fascinating read.
Malay Magic: https://www.gutenberg.org/ebooks/47873
Malay Poisons, charm cures: https://archive.org/details/Malaypoisonscha00Giml
There are also quite a few contemporary Filipino books on their monsters!