NAPLES, November 23, 2013 (AFP) - Gulbis shook off a watery bogey at the par-five first hole at Tiburon Golf Club and carded eight birdies in a seven-under 65.
It was her best round since the final day of the 2012 Kraft Nabisco Championship, and Gulbis said it was the product of recent hard work with coach Butch Harmon on getting used to some new irons.
"As any player knows it's quite a process to change irons and switch to the new TaylorMade irons and just spent a lot of time with Butch redoing every aspect of my game and just working on fundamentals," she said.
Gulbis is seeking to add a second LPGA title to a resume that includes a victory at the 2007 Evian Masters.
Piller and Pornanong are both fighting for a first career LPGA title, although the Thai golfer won the unofficial HSBC Brasil Cup last season.
Piller, like Pornanong, notched five birdies in her five-under 67 to join the leading trio on 11-under par 205.
They were two strokes in front of a group of four players on 207 that included overnight leader Sandra Gal of Germany, China's Feng Shanshan and Americans Stacy Lewis and Lexi Thompson.
Lewis, the world number three who is leading the race for the Vare Trophy for low scoring average as the LPGA season concludes with this elite event, climbed up the leaderboard with a tournament record 63.
A win in the tournament offering a $700,000 winner's prize would also see Lewis move past world number one Park In-Bee and Norway's Suzann Pettersen to claim the LPGA money title.
Lewis jump-started her round with an eagle at the par-four third, and her eight birdies included six in the span of seven holes on the back nine.
Feng had six birdies in a five-under 67, while Thompson had five birdies and no bogeys in her five-under effort.
Gal, the leader after each of the first two rounds, struggled to a two-over 74. Her double-bogey six at the par-four second was followed by a bogey at the fourth and a birdie at the seventh, and the German parred her way in from there.
American Michelle Wie carded a 66 and was alone on 208, one stroke in front of a group that included South Korea's Park.
New Zealand teenager Lydia Ko, playing her first tournament as a professional after four wins in pro events as an amateur, carded an even par 72 and was in a group on 214, nine shots off the pace.
Leading third-round scores on Saturday in the LPGA Titleholders (USA unless noted, par-72):
205 - Natalie Gulbis 70-70-65, Gerina Piller 71-67-67, Pornanong Phatlum (THA) 70-68-67
207 - Stacy Lewis 71-73-63, Feng Shanshan (CHN) 66-74-67, Lexi Thompson 66-74-67, Sandra Gal (GER) 64-69-74
208 - Michelle Wie 72-70-66
209 - Azahara Munoz (ESP) 72-68-69, Park In-Bee (KOR) 68-72-69, Cristie Kerr 69-69-71, Yoo Sun-Young (KOR) 68-68-73
210 - Amy Yang (KOR) 73-68-69, Ryu So-Yeon (KOR) 70-71-69, Jennifer Johnson 71-69-70
211 - Mika Miyazato (JPN) 70-73-68, Meena Lee (KOR) 69-72-70, Sandra Changkija 67-74-70, Park Hee-Young (KOR) 69-70-72
212 - Angela Stanford 74-69-69, Karrie Webb (AUS) 70-73-69, Chella Choi (KOR) 71-70-71, Ayako Uehara (JPN) 69-72-71
213 - Morgan Pressel 71-68-74
214 - Cindy LaCrosse 69-76-69, Jane Park 68-77-69, Brittany Lang 68-76-70, Lydia Ko (NZL) 71-71-72, Anna Nordqvist (SWE) 66-73-75