LPGA champion Pace had three bogey-birdie combinations on her way to an even-par 71.
Starting on the back nine at the Evian Resort Golf Club., the Pearl Valley golfer dropped at 12 but birdied 13 and parred her way to the turn.
On the homeward stretch, the two time Investec Cup for Ladies winner bogeyed six, but birdied seven and negated a bogey at 12 with a birdie at the next hole.
She finished five strokes behind the joint the leaders in a tie for 26th.
Thompson made an explosive start and picked up three birdies and an eagle at the par-five 13th in a four-hole stretch.
The 20-year-old American parred her way home to a flawless five-under-par 66 to set the clubhouse target, but 22-year-old Lee matched her score in the afternoon.
The South Korean mixed seven birdies with two bogeys, collecting five of her gains on the back nine.
World number one Inbee Park from South Korea is also well off the pace at one over 72.
World number two Lydia Ko, who is attempting to become the youngest player to ever win a women’s Major, signed for a 69.
Meanwhile it was a very tough day at the office, though, for fellow South African first-timers Paula Reto and Connie Chen.
FIRST ROUND LEADERBOARD (top 10)
66 Lexi Thompson USA; Mi Hyan Lee KOR
67 Eun-Hee Ji KOR; Pornanong Phatlum THA; Gerina Pillar USA
68 Minjee Lee AUS; Nicole Broch Larsen DEN; Beth Allen USA; Shanshan Feng JAP, Sei Young Kim KOR
Written and released by Lali Stander on behalf of the Sunshine Ladies Tour and WPGA.
