Shamim's three-day total of 12-under-204 placed him in the joint lead along with Kolkata's Shankar, who shot a two-under-70 today at the Digboi Golf Links.
Rookie Karan Taunk of Jamshedpur was two shots off the lead in third place.
Shamim (69-69-66), a winner of nine titles including seven on the PGTI, moved up from overnight tied fifth to joint first thanks to his superb third round effort of 66 which was incidentally the day's best score.
The 36-year-old currently ranked 22nd on the Rolex Rankings had an eventful back-nine. He missed a couple of short putts for bogeys on the 10th and 12th but kept his rhythm going with birdie conversions from 15 feet and 30 feet on the 11th and 13th.
Shamim, trailing for most part of the day, caught up with leader Shankar after a magnificent eagle-two on the 14th, where he drove the green, and a chip-in for birdie on the 17th.
Shankar (65-69-70), the overnight leader by two shots, slipped into the joint lead after a steady 70 on the penultimate day. The two-time winner at Digboi chipped-in for eagle from 25 yards on the seventh and added two more birdies to his card by landing it within two feet on the fourth and 12th. Two missed opportunities from close range meant the 31-year-old dropped bogeys on the second and 14th.
Sri Lankan N Thangaraja occupies fourth position at nine-under-207 while Kolkata's Mohammad Sanju is placed fifth at seven-under-209.
Defending champion Kunal Bhasin of Australia lies tied 36th at four-over-220.
