World number three Stacy Lewis birdied her last two holes to lead the LPGA Thailand by three strokes at the end of the first round.
After dropping a shot for the first time on Thursday at the 16th hole, Lewis birdied the 17th and 18th to card a nine-under 63, giving the 28-year-old American a three-shot cushion over France's Karine Icher.
Lewis kick-started her opening round with an eagle on the par-four 3rd, before three-straight birdies from the 5th hole took her to five under.
Another five birdies followed for Lewis, including two in a row to complete her round.
Icher produced a bogey-free 66 to slot in behind Lewis, birdying the 18th hole to move clear of a group of four players on five under.
The 34-year-old Frenchwoman notched consecutive birdies on two occasions on the front nine to be four under halfway around the Siam Country Club's Pattaya Old Course and then birdied the 13th and 18th holes to finish the opening day on six under.
Catriona Matthew of Scotland, South Korean pair Amy Yang and Park Inbee, and the USA's Gerina Piller all carded five-under 67s to be tied for third ahead of Friday's second round.
After scoring an eagle on the first hole, Piller was on track for a brilliant opening day when she finished the front nine on five under.
But after another birdie on the 10th hole, the 27-year-old American struggled on the back nine, bogeying the 14th and 17th before birdying the last to finish the day on five under.
The quartet tied for third are followed by Spain's Beatriz Recari, Ryu So Yeon of South Korea and the USA's Lizette Salas on four under, while there is a group of 10 players a further shot back including Australian veteran Karrie Webb and New Zealand youngster Lydia Ko.
World number one Yani Tseng had a terrible first round in Chonburi, carding five bogeys in her three-over 75, which leaves her six positions off the bottom of the leaderboard.