Peter Uihlein continued his impressive form since recovering from a wrist injury to set a daunting clubhouse target in the first round of the True Thailand Classic on Thursday.
Uihlein was forced to withdraw from the Omega Dubai Desert Classic last month due to the problem, but returned to action at the Maybank Championship Malaysia two weeks later and finished ninth in Kuala Lumpur.
The former European Tour rookie of the year then finished fourth in the Perth International and carried that form into the opening day in Hua Hin with a brilliant 64 at Black Mountain Golf Club.
Starting on the back nine, Uihlein birdied his first two holes and recovered from a bogey on the 12th with birdies on the 13th, 16th and 17th to reach the turn in 32.
Four more birdies completed a matching front nine of 32 and left the 26-year-old American on eight under par, two shots ahead of Scotland's Scott Jamieson and Spain's Javier Colomo.
Jamieson also started from the 10th and followed six straight pars with five birdies in succession from the 16th on his way to a flawless 66 which was matched by Colomo.
Home favourite Thongchai Jaidee, who spent three days in a Bangkok hospital with a virus which forced him to withdraw from the Maybank Championship Malaysia and miss last week's WGC-Cadillac Championship, was five shots off the pace after a 69 as he looked to go one better than last year's second place.
Defending champion Andrew Dodt was among the later starters and was level par after three holes, while fellow Australian Jason Scrivener had recorded the 11th hole-in-one of the season with an ace from 163 yards on the third in his 72.