Thangaraja was joined by Bengaluru golfer Khalin Joshi, who struck a three-under-69 in round three, in tied first place at seven-under-209 at the Royal Calcutta Golf Club.
Ajeetesh Sandhu of Chandigarh matched Thangaraja's day's best of 67 to jump into contention in third place just one shot behind the joint leaders at the Rs. 30 lakh event.
Eighteen-year-old Feroz Singh Garewal, another Chandigarh-based professional, achieved the rare distinction of making consecutive eagles during round three.
Joshi (71-69-69), also a winner of two titles on the PGTI, made a move from overnight tied fourth to joint first thanks to a timely 69. Joshi landed his wedges within a couple of feet for two birdie tap-ins on the front-nine. He also recovered well from the bunker wall to birdie the 15th after a 20-feet conversion.
Also Read
Round two leader Feroz Ali Mollah of Kolkata dropped to tied fourth after his third round of 75. Bengaluru's C Muniyappa and Gurgaon's Shubhankar Sharma shared fourth place with Feroz at five-under-211.
Reigning Indian Open champion and local lad SSP Chowrasia scored a 74 to end the day in tied 35th at four-over-220.
Garewal produced one the highlights of the day when he achieved one of the rarest feats in golf. He sank back-to-back eagles on the eighth and ninth. What made his achievement even more special was the fact that both his eagles were eagle-twos that came on par-4s.
He ended the day with a 73 to be placed tied 39th at five -over-221.