Pat Perez fired a three-under-par 69 Sunday to win the CIMB Classic in Malaysia by four strokes, firmly eclipsing two-time defending champion Justin Thomas to claim just his third career title.

Perez finished with an aggregate score of 264 at par-72 TPC Kuala Lumpur, ahead of second-placed Keegan Bradley with Xander Schauffele and Kang Sung-Hoon seven off the pace in joint third.

Perez ended a seven-year trophy drought at last year's OHL Classic and now, in his 403rd start on tour, the 41-year-old American becomes the CIMB's oldest winner.

But there was disappointment for Thomas, the PGA Championship title-holder and 2017 PGA Tour Player of the Year, who finished tied for 17th despite a 67 in the final round of his title defence.

Perez, who shot rounds of 66, 65, 64 and 69, relished his latest victory, particularly as he did not play for months at the start of 2016 while recovering from shoulder surgery.

"I was so excited to come back after, you know, being out for so long," he said.

"I did not think I was going to win this week... I putted unbelievable really. I didn't hit it that great."

In sweltering conditions, Perez, who led since Friday's second round, birdied three of the first four holes on Sunday to maintain his four-shot overnight lead.

He seemed surprised by the turn in fortunes so late in his career, describing himself as a "late bloomer", but vowed he would not change his lifestyle.

"I'm not going to change anything -- I'm still not going to work out. I'll still have a bad diet and I'm going to enjoy myself," he said.

Thomas said he "ran out of gas" after coming into the tournament off a superb season.

"I was definitely low on gas. It's been a great but a long year," he said.

"I really played well the last two days, which was nice to see. I just didn't make enough putts and didn't capitalise on enough opportunities to have a really good finish."

The 24-year-old American had a breakthrough season in 2016-17, racking up five wins including his maiden major victory.

Other favourites at the CIMB also fared poorly, with Japan's Hideki Matsuyama finishing tied for fifth and India's Anirban Lahiri tied for 10th.

Perez gets the $1.26 million prize purse and 500 FedEX Cup points for his win. The $7 million CIMB Classic is co-sanctioned by the PGA Tour and Asian Tour.

Source: AFP