The Indian, who began the day with a two-shot lead at the top, carded a one-under-par 71 today at the event sanctioned by the Asian Tour and Professional Golf Tour of India.
His three-day total of 11-under-par 205 gave him a slim advantage over holder Wade Ormsby (70) of Australia who shared second place with Bangladeshi Siddikur Rahman (69), Indian teenager Shubhankar Sharma (68) and Mithun Perera (69) of Sri Lanka.
After opening with a birdie, Gangjee struggled on the greens and had to battle-tooth-and-nail to stay in contention to end a 10-year title drought on the Asian Tour.
"I was not tense because that's what most people are thinking. I did not hit the shots and that is what I did not like about the entire day. Overall, I hang in there today so tomorrow will be a lot better," said the 36-year-old Gangjee.
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"I hit a bunch of great putts but I had tricky lines so I got a bit unlucky today. I'm still in it with a chance so it will be about holding my nerves on the last 18 holes," said Gangjee.
Australia's Ormsby chipped-in for birdie on the 12th hole from the edge of the green and was thankful to escape with a bogey on 15 after his approach shot landed in the jungle. A birdie on the last hole put him within reach of retaining his title.