The 29-year-old former caddie carded a nine under-par 279 on the demanding course, ahead of second-placed Irishman Damien McGrane.
McGrane shot 70 after briefly sharing the lead with the Indian on the front nine before aggregating seven-under for the tournament, co-sanctioned by the European and Asian tours.
Spain's Jose Manuel Lara came third after his par 72 final round earned him a five-under 283. French overnight leader Raphael Jacquelin tied fourth after a two-over 74 with India's Digvijay Singh, a further shot behind.
South African world number four Ernie Els was tied sixth at three-under par 285 with Thomas Bjorn of Denmark, India's Gaurav Ghei, Maarten Lafeber of Netherlands and Britain's Ross McGowan.
The diminutive Chowrasia, who started two shots off Jacquelin tied at fifth overnight, carded four birdies in his front nine to go two strokes clear.
McGrane, tied second overnight at five-under 211, came into joint lead after six holes only for Chowrasia to take a decisive advantage after a stunning 25-foot putt for a birdie two on the seventh hole.
The Irishman's hopes evaporated after he bogeyed the seventh and 10th holes and another dropped shot on the 17th gave Chowrasia a three-shot cushion. He played safe to clinch the biggest victory of his career.
(Reporting by N.Ananthanarayanan; Editing by John Mehaffey)
