While I know little on firearms overall, it seems to me that (from what examples I can find online) the 'pistol butt' style, if you took away the 'stock' has a certain resemblance to a traditional Japanese matchlock.
There was of course certain Japanese presence in SE Asia. I recall years ago finding examples of Japanese katana among swords of India. It seems in many discussions, there have been mentions of Japanese throughout these regions.
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