The Derby-born player posted the seventh ace of her career on the par-three 11th at Pinnacle Country Club.
Reid carded a six-under-par 65 to finish in a tie for second, behind South Korea's Park Sung-hyun.
The 29-year-old sits alongside South Korean Ryu So-yeon and America's Ally McDonald.
Fellow Briton Felicity Johnson finished behind them after a five-under 66.
"As soon as I hit it I thought, oh, it's got a chance," Reid told lpga.com. "It just pitched a little longer than we thought. But yeah, I mean, a hole-in-one, I hit a good shot there."
Park, who has not missed a cut since she joined the LPGA tour at the start of the 2017 season, hit a stretch of six consecutive birdies to take the early clubhouse lead.
Reid, a five-time winner on the Ladies European Tour, is making her Arkansas Championship debut.
Britain's Mel Reid hit a hole-in-one to put herself within two shots of the early lead at the NW Arkansas Championship.