In-form Anirban Lahiri carded a bogey-free six-under 66 to finish tied sixth, his sixth successive top-10 finish on Asian Tour.
Gangjee (65) totalled 19-under, the best total of his career, and Lahiri was 17-under. Another Indian SSP Chowrasia (67) was tied 11th at 14-under at the event jointly sanctioned by the Asian Tour and European Tour.
Jeev Milkha Singh (72) and Chiragh Kumar (74) were tied 64th at three-under 285 each.
He was also second at 2006 Mercuries Taiwan Masters.
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For Lahiri, the top-ranked Indian golfer in the world, it was his sixth successive top-10 finish on Asian Tour since Thailand Golf Championships and he has not finished outside top-12 since the Indonesian Open last December.
Meanwhile, up at the top, Chile's Felipe Aguilar blazed home with a birdie-eagle finish to set the clubhouse target of 22-under 266 and it earned him his second European Tour title, six years after he won the first in Indonesia in 2008.