GUADALAJARA, November 15, 2013 (AFP) - Ryu and Nordqvist finished with birdies at the par-5 18th while Pornanong could muster only a par, leaving them tied on nine-under-par totals of 135 at Guadalajara Country Club.
American 18-year-old Lexi Thompson, who fired the day's low round with a 64, shared fourth on 136 with compatriot Gerina Piller and world number one Park In-Bee, who is trying to become the first South Korean to claim LPGA seasonal Player of the Year honors.
Ryu, the 2011 US Women's Open champion, played the front nine level but opened the back nine with back-to-back birdies and birdied 14 and 16 as well as the last.
Ryu's playing partner Nordqvist opened with a birdie, followed with her only bogey at the third, then birdied the seventh and back-to-back birdies at 11 and 12 plus another at 15 allowed her to close with a birdie.
"It's just a fun atmosphere," Nordqvist said. "You just try to keep up and you know feed off of each other and give yourself a lot of chances for birdies."
Pornanong had back-to-back birdies at the par-3 sixth and seven, then answered her lone bogey at the eighth with a birdie to close the front nine. She fired eight pars and a birdie at the 16th on the back side.
"Today, I'm very happy with my score, but the putting was not very good today. I just missed a few short putts," Pornanong said.
The 23-year-old Thai standout won the unofficial LPGA Brasil Cup last year and was runner-up this year at Mobile Bay.
Scores on Friday after the second round of the LPGA Lorena Ochoa Invitational (USA unless noted, par 72):
135 - Anna Nordqvist (SWE) 68-67, Ryu So-Yeon (KOR) 68-67, Pornanong Phatlum (THA) 66-69
136 - Lexi Thompson 72-64, Gerina Piller 71-65, Park In-Bee (KOR) 68-68
137 - I.K. Kim (KOR) 70-67, Lizette Salas 70-67
138 - Stacy Lewis 72-66, Karine Icher (FRA) 70-68, Suzann Pettersen (NOR) 70-68, Jenny Shin (KOR) 69-69
139 - Morgan Pressel 73-66
140 - Lee Il-Hee (KOR) 74-66, Jessica Korda 72-68, Azahara Munoz (ESP) 71-69, Amy Yang (KOR) 67-73
141 - Paula Creamer 74-67, Carlota Ciganda (ESP) 72-69
142 - Jodi Ewart Shadoff (ENG) 75-67, Chella Choi (KOR) 74-68, Mo Martin 73-69, Ai Miyazato (JPN) 70-72, Michelle Wie 69-73
143 - Brittany Lincicome 76-67, Brittany Lang 71-72
144 - Cristie Kerr 77-67
145 - Catriona Matthew (SCO) 74-71
146 - Meena Lee (KOR) 74-72, Caroline Hedwall (SWE) 73-73, Sandra Gal (GER) 72-74
147 - Margarita Ramos (MEX) 75-72, Angela Stanford 75-72
148 - Alejandra Llaneza (MEX) 75-73
149 - Beatriz Recari (ESP) 72-77
151 - Taylor Collins 74-77