Australian Adam Scott fired a two-under-par 70 on Thursday to sit six shots off the lead but countryman Aaron Baddeley's 67 moved him to within three strokes of the frontrunners after the first round of the PGA Tour's CIMB Classic in Kuala Lumpur.
Scott, who finished a stroke behind winner Justin Thomas last year, is one of 18 players tied for 26th on a bunched leaderboard.
Thomas and fellow Americans Derek Fathauer and Keegan Bradley all shot impressive opening rounds of eight-under 64 to set up a three-way tie for the lead.
Englishman Paul Casey birdied four of the last five holes to lie one shot behind the American trio in fourth, one clear of Anirban Lahiri of India.
Baddeley completed a five-under-par opening round of 67 to share sixth place with three players including Spain's Sergio Garcia, whose round featured a 22-foot eagle putt on the third.
Of the other Australians, Marc Leishman is well placed after a three-under 69. Scott Hend went around in two-over 74, one better than John Senden and Marcus Fraser.
Casey, chasing a first PGA Tour win since 2009 and finishing in the top four in his past four tournaments, shot a 65.
He dropped a shot on the par-5 third but was two under at the turn following gains at the fifth, seventh and ninth holes.
Further shots were picked up on the 11th and 14th before three successive birdies rounded off a solid start.
Thomas had nine birdies in his round, with a bogey on the sixth his only blemish.
Fathauer was flawless in his 64 while Bradley birdied six of the first eight holes before eagling the 10th.
Dropped shots on the 11th and 13th checked his momentum but he recovered with birdies at 16 and 17.
England's Ian Poulter, on his return from a foot injury, shot a one-under 71.
