Stephanie Meadow was two shots off the pace after round one of the Kia Classic in Carlsbad.
The Northern Irishwoman carded an opening round of 67 to leave her chasing leader Chella Choi.
Meadow completed a blemish-free day with five birdies, while Choi birdied the final three holes to top the leaderboard on seven-under 65.
The Jordanstown native made her mark on the professional game over four years ago with a third-place finish in her first major, the 2014 US Women’s Open.
A 15-strong group made up the chasing pack in third place, a shot further back than Meadow, while England’s Mel Reid sandwiched a bogey on the par-five eighth hole with two birdies to finish in 26th on two under.
Jodi Ewart Shadoff and Bronte Law both had to settle for rounds of 72, each making three bogeys.