Hi Jens,
I think this is an outstanding question, and I cannot recall any references that would suggest export of such raw materials from these regions. As you have noted, the smelted ingots of metal from Sri Lanka and India are well known in history as sources to major sword blade centers. It seems even in ancient times the metal resources for sword blades came from these regions. I will have to search the reference, but I believe I once saw reference to 'Chinese' steel...but I would think that may refer to the Sri Lankan product which may have been transported via trade routes referred to generally as 'China'. In what is now Viet Nam, the region of Cochin was often referred to as 'Cochin China' in the 19th century, possibly earlier ( Dha guys help me out on this
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As Mark has said, it would seem that Indonesian and Malaysian regions would have relied on imports primarily for weapons production.However,the reference that Rick has posted on prehistoric iron production in Borneo might put some interesting perspective on this.
Again, I think this is a fascinating question and I hope we can get some more responses with more information.
Best regards,
Jim