Certainly Indo-Malay, but fact of the matter is that once you have narrowed it down to that, a more specific id becomes a little tricky, as similar spears/tombaks can be found all over the archipelago.
Based on the beefy-ness of this one, and on other similar ones I have and have seen, I'd say this one is from Borneo or Sumatra.
Should clean up to be a superb piece. Nice find!
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