Chawrasia had finished second in the Asian Tour co-sanctioned event four times, including a playoff defeat to Lahiri last year.
Yet the 37-year-old, who won the 2008 Indian Masters and the Panasonic Open India on the Asian Tour two years ago at the Delhi Golf Club, held his nerve for a final-round one-under-par 71 to claim victory by two shots.
Lahiri birdied the first three holes of the day and was tied for the lead after Chawrasia dropped a shot on the sixth.
Chawrasia, however, wrested back the advantage with a birdie on the eighth and finished with a four-day total of 15-under while South Korean Wang and Lahiri finished on 13-under.
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The win allowed Chawrasia to reclaim his European Tour playing privileges, which he lost last season after finishing 113th in the Race to Dubai.
"This is very important for me because I get a full card and most probably I'm playing the Olympics and the World Cup also," Chawrasia told reporters.
Filipino Angelo Que carded a spotless 65 to finish a shot further back on 12-under for a share of fourth spot with Brazil's Adilson da Silva.
(Reporting by Sudipto Ganguly in Mumbai; editing by Toby Davis)
