Stacy Lewis held on to lead Amy Yang by one stroke at the LPGA Thailand despite a dismal third-round 73 on Saturday.
Leading overnight by three shots, after a second-round 64, Lewis had three straight bogeys in the front nine before the American fired a five-foot eagle on the 15th hole to regain the lead from South Korea's Yang.
Lewis, the world No. 3, had five bogeys, including at the 18th, one eagle and two birdies at the Siam Country Club Pattaya Old Course. She has a three-day total of 13-under 203.
Sandra Gal of Germany is third, a further stroke behind Yang.