Tony Finau turned in 32 to take a share of top spot alongside overnight leader Patrick Reed on day two of the WGC-HSBC Champions.
Slightly calmer winds than during round one at Sheshan International Golf Club allowed for some low scoring and Finau was at the forefront as he moved to ten under.
Reed would not be left behind, however, and he birdied two of his first four holes to get himself into double-figures as the leading pair threatened to pull away from the field.
Fellow Americans Xander Schauffele and Patrick Cantlay were four shots back, one clear of defending champion Justin Rose, fellow Englishman Tommy Fleetwood and American Keegean Bradley.
Finau got within one of the lead as he took advantage of the par five second and a 15-footer on the fourth then gave him a share.
Kiradech Aphibarnrat was a picture of consitency and the reigning ISPS Handa World Super 6 Perth champion made birdies on the par five second and eighth to join the group in second.
That was soon three back, however, as Finau got up and down from the sand on the driveable par four seventh, holing a ten-footer to hit the front on his own.
Reed was among the late starters but it did not take him long to reclaim a share of the lead, playing a wonderful short pitch to set up a birdie on the second.
An Aphibarnrat bogey on the ninth saw him turn in 35 and that left just two players within three of the lead.
One of those was Cantlay, who recovered from a bogey on the first with birdies on the third, fifth, sixth, eighth and ninth to turn in 32.
Schauffele had been the other one but after seven straight pars to open, he birdied the eighth to get within two of the leaders.
The par fives were bearing fruit for most of the field and Fleetwood - in the final group of the day - birdied the second to join Aphibarnrat at five under.
Finau continued that theme with a birdie at the eighth to get to double-figures but Reed's approach to the third was to eight feet and the duo were tied once more.
Bunker trouble for Schauffele on the ninth dropped him to six under and the leading pair were four ahead of the rest of the field.
Aphibarnrat made a second consecutive bogey on the tenth to drop back and he was replaced at five under by Rose, who birdied the second and holed an eight-footer at the third.
Thai Aphibarnrat, Spaniard Rafa Cabrera Bello, New Zealander Ryan Fox, England's Tyrrell Hatton and Ian Poulter, Americans Billy Horschel and Pat Perez, and Australian Adam Scott were four under.
