The bogey-free effort gave the Las Vegas born 36-year-old a three-shot lead over Japan's Hideki Matsuyama in the $7 million co-sanctioned Asian Tour event, the third of the new 2016 PGA Tour season.
Piercy, the world number 42 said a hot putter had been the difference on Thursday after a solid but unspectacular tied 25th finish in Nevada last week.
"I was really frustrated, especially being at home. I felt like I played absolute worst I could have played and still finished top-25," he told reporters of last week's efforts.
"The putts didn't go in last week and lo and behold this week, filled them up pretty good on first day. So, hopefully it continues."
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While Piercy was dominating the leaderboard, compatriot Scott Brown was picking up the big prize. The 32-year-old walked away with a new sports car after a hole-in-one at the par three 15th.
"I made like three hole-in-ones in the last two years on Tour and walking up looking at the card I thought, man, it would be nice to make a hole-in-one and win something. Because the other three I made I got nothing," Brown said.
"It was 186 to the hole. It was kind of a weird number for me. I was kind of right in between a 6-iron and 7-iron and chose to go 6-iron, took a little off of it and it never left the flag. It hit probably 10 feet short and rolled right in."
It helped improve his first round mark to four-under 68, good enough for a share of 16th alongside major winners Adam Scott of Australia, Ireland's Padraig Harrington and Stewart Cink of the U.S.
The CIMB Classic had been previously played on the Mines Course in the Malaysian capital but the short track proved a birdie fest for the U.S. circuit's finest.
But the Kuala Lumpur Golf and Country club, which is hosting for the third time, failed to halt the red numbers with 62 of the 78-man field under par for the first round.
Former U.S. PGA champion Keegan Bradley was one who found picking up shots straight forward on Thursday as he fired seven birdies and an eagle in a round of 66 to share third spot behind Piercy and Matsuyama.
American Ryan Moore, winner of the event in the last two years, was well placed in a tie for eighth at five-under.
(Writing by Patrick Johnston in Singapore; editing by Sudipto Ganguly)
