Curtis, a Korn Ferry Tour player, also caddied for his sister in 2018 when she won the season-ending event.
“If we’re both home we are always playing golf together and joking around,” Thompson said. “It’s great to have him out here. I really appreciate him helping me out and keeping me loose out there. Whether I play good or bad, he always keeps a smile on my face.”
On Thursday after early morning rain, Thompson birdied five of the first seven holes. She played the next nine holes in even par with a birdie and a bogey, then birdied the final two holes. The 11-time LPGA Tour had her lowest score of the year a week after missing the cut in Houston in the U.S. Women’s Open.
“I was just overall very happy with how I committed to my shots,” Thompson said. “That’s what I’ve really been working on. I’ve been working so hard on my game in general trying to improve on it, and it’s been kind of an up and down roller coaster with an unfortunate week last week.”
Nanna Koerstz Madsen of Denmark was a stroke back after a bogey-free round.
“I was a little shaky on my driver going into the event, and putting as well actually. So now it is always nice to start off with a good round,” Koerstz Madsen said. “I don’t have any expectations. I just want to go out and play and see if I can do good mentally.”
Defending champion Sei Young Kim was at 67 with Caroline Masson and Megan Khang.
Masson holed a 9-iron approach for eagle on the par-4 13th.
“I had a pretty good number for a 9-iron, a little downwind, and kind of hit the shot I wanted,” Masson said. “It pitched on top and just released a little bit. I kind of wasn’t really looking anymore because I thought it was good, but I didn’t realize it would go in.”
Tiburon was the site of the PGA Tour’s QBE Shootout last week. In a normal year, the CME Group Tour Championship is held before Thanksgiving.
“I think pretty similar,” Kim said. “Greens are softer. I think last night we got a little bit of rain, the greens so feel like little softer than yesterday. But, yeah, everything very similar.”
The $1.1 million winner’s prize, down from $1.5 million last year, is still the largest in women’s golf.
Top-ranked Jin Young Ko was at 68 with Minjee Lee, Maria Fassi, Anna Nordqvist, Carlota Ciganda and 2014 champion Cristie Kerr.
After spending most of the year in South Korea, Ko tied for second at the U.S. Women’s Open to qualify for the event. She had a double bogey on the par-4 third, her 12th hole of the day.
Kerr dislocated three ribs in a golf cart accident before the start of Volunteers of America Classic two weeks ago, and fought through pain to tie for 23rd in Houston.
“I feel a little bit better today, but I just thought it was really important to get through last week,” Kerr said. “There were points where I didn’t think that I was going to be able to, but I guess when they say there is a will there is a way.”
Race to CME Globe leader Inbee Park and second-place Danielle Kang each shot 71, playing alongside Kim. Kang led the points race since back-to-back wins in Ohio until Park took over the lead last week.