In his first tournament as a full-time PGA member, Kiradech Aphibarnrat carded an opening three-under-par 69 to be in a tied for 26th place at the US$7 million PGA event in Kuala Lumpur on Thursday.
The world No 37, the only Thai in the event, fired four birdies against a lone bogey to finish six strokes behind unfancied leader American Bronson Burgoon.
The 31-year-old American had eight birdies, an eagle on the 18th with a bogey on the 13th.
Burgoon, still looking for his maiden PGA win, has a one-shot advantage over countryman Austin Cook, who produced eight birdies in a bogey-free round to have sole possession of second.
Burgoon outshone Ryder Cup stars Justin Thomas and Paul Casey as he shot nine-under par 63 to lead the event and then played down his round as "boring".
At the revamped TPC Kuala Lumpur, Burgoon chipped in for an eagle on the 18th hole, his ninth after starting from the 10 tee, and then added five birdies on his back nine.
That gave him a one-shot lead over compatriot Austin Cook on a low-scoring first day, with the red-hot Billy Horschel in a three-way tie for the third place at seven-under par.
Thomas, the two-time CIMB champion and former world one, shot four birdies in his last five holes to move to three shots behind the leader, tied sixth at six-under par along with seven other players including England's Casey.
"I drove it well and I putted pretty good, so it was kind of boring golf, but that's always a good thing," said the Texan.
"I chipped in for eagle from the bunker on my ninth hole, which kind of boosted me, then I just kept going."
World number four Thomas, winner of the event in 2015 and 2016, was happy with his start, especially the finish to his round.
"It was a good day. Kind of up and down. I got off to a good start and then kind of stalled out a little bit there in the middle," said the man with eight PGA Tour wins in the last two seasons.
"I hung in there and just really didn't hit my irons very well. I just didn't take advantage of a couple opportunities, but kind of found something there those last five holes and was able to at least make a good round of it today."
Horschel continued from where he left off in the FedEx Cup playoffs, where he finished inside the top-three in four starts and withdrew from the fourth.
Defending champion Pat Perez opened with a two-under-par 70 in the tournament jointly sanctioned by the PGA and the Asian Tours.