He defeated M Dharma of Bengaluru on the second play-off hole after the two ended the regulation 72 holes with identical totals of 12-under-268 at the Bombay Presidency Golf Club in suburban Chembur.
Delhi's Honey Baisoya, Noida's Gaurav Pratap Singh and Abhinav Lohan of Faridabad were joint third at 11-under-269.
Bengaluru's Udayan Mane was placed sixth at 9-under-271.
Lucknow's Vijay Kumar, who was overnight tied second, slipped to tied 14th after his poor final round of 74.
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The 32-year-old, who began the day in tied second place, one behind overnight leader Dharma (69-67-63-69), missed putts from six to seven feet on the 18th and the first play-off hole, for birdie and par respectively.
Later he converted a tricky six-footer for birdie on the second play-off hole to lift the CG Open title for the second time after 2007.
Earlier in the day, the 2007 and 2010 Rolex Ranking champion capitalised on the first and fourth, both par-5s, with birdies. He also set up a tap-in birdie on the fifth before dropping his first bogey on the sixth.
Ashok then missed some short putts to concede bogeys on the 14th and 15th even as Dharma fought back to be all square by the 17th despite mixing two birdies with three bogeys from the 13th onwards.
Both the players then bogeyed the first extra hole
with Ashok making another three-putt. However, Kumar hung on to grab the decisive birdie on the second extra hole from six feet even as Dharma made a par there after finding the bunker twice.
"I would like to thank my good friend and fellow professional Rashid Khan for all his support. He has helped me get my game back on track as he keeps advising me on my short-game.
"I generally play better on the back-nine here but today my putting form deserted me and I struggled with short putts on the back-nine. After missing those opportunities towards the end, I told myself that I had nothing to lose and should just enjoy myself and stay in the present. That's what kept me relaxed. The fact that I had won at the BPGC in the past also gave me the belief going into the playoff," he said.
His winning cheque of Rs 15,00,000 helped him leapfrog from 49th place to sixth position in the Rolex Ranking as his season's earnings now stand at Rs 18,00,065.
Dharma's second place propelled him from 29th to ninth place. Chikkarangappa S of Bengaluru continues to lead the ranking with earnings of Rs 26,37,440 for the season.
Ashok has numerous triumphs on the Indian circuit but this was his 12th win on the PGTI. He is only second to Mukesh Kumar in the list of PGTI wins. Mukesh has won 16 tournaments on the PGTI so far.