KUALA LUMPUR, Malaysia -- Defending champion Justin Thomas endured a terrible start to the third round of the CIMB Classic after the American faltered with three bogeys and a double-bogey to finish with a 1-under 71 on Saturday.
He was swiftly overtaken by Anirban Lahiri, who shone at the TPC Kuala Lumpur with nine birdies for a 65 to open up a four-shot lead going into the final round Sunday.
Thomas had two bogeys and a double-bogey in the first three holes of the back nine.
"It was really just terrible golf for the first 13 holes. To be 4 over par out here, it was a very weird feeling. I don't know," he said.
At least the 23-year-old Thomas ended the penultimate round with five consecutive birdies.
"It was great to have that finish," Thomas said. "I feel like that showed a lot of me, and I hope that I can ride the momentum into tomorrow."
Lahiri's low score positioned him at 19 under, a mark that could have been better if not for a double-bogey on the 12th hole in an otherwise flawless scorecard.
"I just told myself that I got rid of my double-bogey early in the round today and just tried to focus on what I needed to do," said Lahiri, who was runner-up at the Asian Tour's Macau Open last week. "You know, like I said, I feel like I'm hitting it good with my irons, my wedges, and I'm putting it good."
Lahiri has only one top-10 finish on the PGA Tour -- a tie for fifth at the 2015 PGA Championship.
Scotland's Russell Knox played another solid round for a 68 and moved into a tie for second with Thomas.
Ryan Moore, the 2013 and 2014 winner, is tied for 17th after managing a 70.
The Associated Press contributed to this report.