Late post, apologies, but here's a photo of a banteng bull possibly from the same area.
This one is no world-beater but the best I could find on the allotted day.
Very sharp horns!!

I had recently been discussing these critters with a safari guide who has survived a few serious charges from banteng just this year:
from his experiences it seems they can be more dangerous than buffalo. ...so I was in a "cautious" frame of mind when sneaking in on this fellow to around 15 metres!
Sat watching him for at least 10 minutes before deciding to take the shot, and had to keep shifting my butt to maintain the bead on his chest
through a narrow gap in the Barringtonia. Lucky the wind held!
He was quartering towards me so the "mad dash" immediately on receiving the heart-shot was straight in my direction!
The second barrel was delivered in a big hurry at perhaps 7 or 8 metres as he rushed past!
It was a little high for the shoulder but caught the spine where it dips down between the shoulder-blades and he virtually somersaulted,
as only a banteng bull at full gallop can!
Spectacular stuff!

John: from your initial post: