Beginning three shots behind Chadha (70), the Nepali No.1 fought his way in contention and scripted a fairytale victory with a superlative effort of five-under 67 on the final day to force a play-off before prevailing on the first play-off hole (18th) with a birdie.
The play-off was necessitated after both the players had finished with a tournament total of 18-under 270.
Meanwhile, Asian Tour star Anirban Lahiri made a brilliant charge but faltered in the final holes to finish third at 17-under. Mukesh Kumar and Ajeetesh Sandhu were tied for the fourth place at 274. Rahul Bajal and Md. Dulal Hossain shared the sixth position at 276.
Anirban was richer by NRs 300,720. Shivaram became the second professional golfer after Deepak Thapa Magar (2007 winner) to win the biggest golf tournament in the country of Nepal.
"I am thrilled about my victory. It has still not sunk in me. I felt elated instantly but a little later when I went to collect my prize, I realized about my achievement," said the champion.