I recently read that Srivijaya employs the pirate tribe (orang laut/lanun) to guard the maritime silk road. I'd like to read more about this, but the only sources that I could find was some Indonesian articles from Historia, national geographic and bit of Wikipedia pages. Maybe you guys can link me some articles/books to read?
I wrote about piracy in Southeast Asia, specifically about the Orang Laut and the Ilanun, here.
However, the answer focused on post 1400, so quite a bit later than the Srivijaya Empire.
Unfortunately, there are no really in depth sources for reading about Srivijaya's naval power that I know of. Not much is known about Srivijaya in general due to a real lack of written records from the empire. Most of what we know is cobbled together from foreign records, especially Chinese, and some surviving inscriptions.