GUADALAJARA, November 17, 2013 (AFP) - The 18-year-old American, who won in Malaysia a month ago, stood on 13-under 203 after 54 holes with Kim on 204 after a 67 and American Stacy Lewis on 205 after firing 67 as well.
"It gives me confidence going into tomorrow, but I know there are a lot of great players right behind me, and I know I have to play well. I know I have to shoot another 4- or 5-under," Thompson said.
"I'm just going to go out with the same attitude and just commit to every shot."
South Korean Ryu So-Yeon was fourth on 206 followed by fellow 36-hole co-leaders Anna Nordqvist of Sweden and Pornanong Phatlum of Thailand, who could each only manage par in the third round.
World number one Park In-Bee, fighting to clinch LPGA Player of the Year honors after a season that included three major titles, was on 208 along with her rival for the prize, Norway's Suzann Petersen, and American Lizette Salas.
Petersen must finish third or better this week to keep Park from clinching the award, while a runner-up finish would assure Petersen could do no better than share the award with her.
Thompson, seeking her third career LPGA title, birdied the second and fourth holes, added another at the seventh and began the back nine with a birdie as well. She added a final birdie on the day at 14.
Kim, the 2010 Ochoa champion, birdied two of the first three holes, then made bogeys at two of the next three before stopping the slide with a birdie at the seventh.
She began the back nine with a birdie and added another at 14, then closed with birdies at the par-3 17th and par-5 18th to stay on Thompson's heels in the 36-player event.
"I had a good start," Kim said. "I made birdie on one and two and I think that kind of helped going forwards. Basically I really like this golf course. I have a good feeling for the course. It's just nice to see the result."
Kim could become the first two-time winner of the Ochoa event, the penultimate tournament of the LPGA campaign.
"Winning is amazing, but, like I said, for me, just being able to play golf and just have fun, that's the first thing. If I can win twice, I mean, why not, I think it would be really great," Kim said.
Lewis birdied 10, 11 and the par-3 13th and closed with birdies at 15 and 18 to stand two adrift.
Scores on Saturday after the third round of the LPGA Lorena Ochoa Invitational (USA unless noted, par 72):
203 - Lexi Thompson 72-64-67
204 - I.K. Kim (KOR) 70-67-67
205 - Stacy Lewis 72-66-67
206 - Ryu So-Yeon (KOR) 68-67-71
207 - Anna Nordqvist (SWE) 68-67-72, Pornanong Phatlum (THA) 66-69-72
208 - Suzann Pettersen (NOR) 70-68-70, Lizette Salas 70-67-71, Park In-Bee (KOR) 68-68-72
209 - Michelle Wie 69-73-67, Azahara Munoz (ESP) 71-69-69
210 - Carlota Ciganda (ESP) 72-69-69, Amy Yang (KOR) 67-73-70, Karine Icher (FRA) 70-68-72, Gerina Piller 71-65-74
211 - Brittany Lincicome 76-67-68
212 - Mo Martin 73-69-70
213 - Morgan Pressel 73-66-74, Jenny Shin (KOR) 69-69-75, Lee Il-Hee (KOR) 74-66-73
214 - Jodi Ewart Shadoff (ENG) 75-67-72, Chella Choi (KOR) 74-68-72, Ai Miyazato (JPN) 70-72-72, Jessica Korda 72-68-74
215 - Caroline Hedwall (SWE) 73-73-69, Cristie Kerr 77-67-71, Brittany Lang 71-72-72
216 - Catriona Matthew (SCO) 74-71-71
218 - Angela Stanford 75-72-71, Paula Creamer 74-67-77
220 - Margarita Ramos (MEX) 75-72-73, Sandra Gal (GER) 72-74-74
221 - Alejandra Llaneza (MEX) 75-73-73, Meena Lee (KOR) 74-72-75
227 - Taylor Collins 74-77-76
WD - Beatriz Recari (ESP) 72-77