Thai veteran Prayad Marksaeng on Saturday shot a six-under-par 66 to take a five-shot lead over countryman Thongchai Jaidee going into the final round of the $750,000 Chiangmai Golf Classic.
Prayad, 47, stretched his overnight two-shot lead by going out in 31, including a chip-in for eagle on the seventh, before completing the back nine in one-under to sit on 18 under at the par 72 Alpine Golf Resort-Chiangmai.
"I have a five-shot lead now and I will play steadily and not be aggressive," Prayad said in comments released by the organisers.
"I think the pressure is on those chasing me. They need to have a good front nine or else they won't be able to catch up with me," he added.
Thongchai, a three-time Asian Tour number one, shot a 69 and is tied in second place with Australian rookie Matthew Stieger.
The Thai star, who needs to win on Sunday to have a chance of qualifying for next month's Masters, blamed his putting for not scoring lower.
"I hit a lot of good shots but the greens are killing (me). They are tough to read.
"Prayad played so well... He likes the course and he's in form. He's got a good chance. I'll try my best but I'll need luck tomorrow."
Stieger shot a fine 68 as he remained bogey-free for the week while Asia's first Major winner Y.E. Yang of Korea carded a 67 for a share of fourth place.
Four-time Major champion Ernie Els of South Africa fired his lowest round of the season with a 66 to move up to tied 15th place, eight shots behind the leader.
Scores after round 3 of the Chiangmai Golf Classic (par 72):
198 - Prayad Marksaeng (THA) 65-67-66
203 - Matthew Stieger (AUS) 68-67-68, Thongchai Jaidee (THA) 69-65-69
204 - Marcus Both (AUS) 71-68-65, Anton Haig (RSA) 72-66-66, Kiradech Aphibarnrat (THA) 71-67-66, Scott Hend (AUS) 68-69-67, Y. E. YANG (KOR) 69-68-67, Digvijay Singh (IND) 67-67-70
205 - Gaganjeet Bhullar (IND) 70-70-65, Boonchu Ruangkit (THA) 70-68-67, Zaw Moe (MYN) 70-67-68, Siddikur (BAN) 69-67-69, Hu Mu (CHN) 66-69-70
206 - Ernie Els (RSA) 69-71-66, Thitiphun Chuayprakong (THA) 68-70-68, Baek Seuk-Hyun (KOR) 69-69-68, Jason Knutzon (USA) 67-69-70, Pawin Ingkhapradit (THA) 67-68-71