Singapore golfer Quincy Quek overcame sweltering conditions to shoot a six-under 66 for the first-round lead of the PGA Tour Series-China's Haikou Championship in the port city yesterday.

Temperatures soared to as high as 35.6 deg C, but he kept his cool to sink seven birdies against one bogey at the Sunac Haikou 3km Golf Club to earn a one-shot edge over Thailand's Gunn Charoenkul (67).

The 32-year-old's only blemish came on the long par-five 18th, which measured nearly 600 yards.

American David Kocher and Chinese amateur Yang Kuang were tied for third on 68.

"I rolled the ball quite well on the greens," said Quek, who was 42nd on the Tour's Order of Merit last year. "I hit a few wedge shots to about three feet early on, so three birdies there on the front nine.

"I holed some longer putts on the back nine and that really helped."

Another Singaporean Abdul Hadi was joint-22nd with a 71.

Golfers observed a minute's silence before the start of the first round to mark their respect for Malaysian golfer Arie Irawan, who died suddenly in his sleep at the Sanya Championship last Sunday.

He was found unconscious by his room-mate Kevin Techakanokboon of Thailand and fellow golfer Shotaro Ban attempted cardiopulmonary resuscitation before medical officials arrived.

The Tour said in a statement on Wednesday that the 28-year-old died of natural causes without any drugs or toxins in his system: "The police and coroner's final report stated that Irawan's death was a sudden death from natural causes in his sleep at the hotel."