Bangladesh's Siddikur carded a third straight four-under-par 68 to claim a one-shot lead over title holder Anirban Lahiri of India at the SAIL-SBI Open in New Delhi on Friday.
Siddikur fired five birdies against a lone bogey at the Delhi Golf Club to lead from Lahiri, who birdied his last two holes for a bogey-free 66.
Joint overnight leader Khalin Joshi battled to a 71 to end the day two strokes back in the $300,000 Asian Tour event, while another local hope Rashid Khan was a further shot behind after also carding a 71.
Thailand's Chapchai Nirat and home hero Shiv Kapur will enter the final day four off the lead after rounds of 67 and 69 respectively while American Chan Kim stumbled to a 74 to fall out of contention.
The 29-year-old Siddikur was delighted with his performance.
"Very consistent. I'm so happy," said Siddikur, who hit 12 fairways and 14 greens in regulation. "I've been very consistent. I'm happy with myself with three 68s. I've been trying to get more regulation play and it's been working."
Siddikur's round was highlighted by a monster 40-foot birdie conversion on 16 but he said a par save on 18 after finding the punishing bushes was crucial as it kept him ahead of the defending champion, Lahiri.
"On 16, I tried to make just a two putt but it went it. It was a fluke. But I made a good save on 18, made a great up and down," said Siddikur, who leads on 12-under-par 204.
Lahiri, 25, who started the day four behind, charged into contention with a superb display of ball striking as he hit 15 greens in regulation. "It's the best I have played all week," he said. "I'm happy with where I am right now."
Scores after round three (par 72):
204 - Siddikur (BAN) 68-68-68.
205 - Anirban Lahiri (IND) 71-68-66.
206 - Khalin Joshi (IND) 66-69-71.
207 - Rashid Khan (IND) 72-64-71.
208 - Chapchai Nirat (THA) 66-75-67, Shiv Kapur (IND) 69-70-69.
209 - Matthew Stieger (AUS) 70-71-68, Chan Kim (USA) 67-68-74.
210 - Pawin Ingkhapradit (THA) 70-69-71.
211 - Antonio Lascuna (PHI) 71-73-67, Adam Groom (AUS) 71-71-69, Boonchu Ruangkit (THA) 72-69-70, Lam Chih Bing (SIN) 73-67-71, Ajeetesh Sandhu (IND) 70-70-71, Thitiphun Chuayprakong (THA) 72-67-72, Chiragh Kumar (IND) 68-70-73.