Jeeno shines on greens to grab LPGA lead at Liberty National
The Thai star said she'd used a week off after a disappointing tie for 24th in the year's first major, the Chevron Championship, to sort out her putting.
It paid off with her lowest round to open a tournament since the 2022 BMW Ladies Championship.
"I think my putter was working well, better than Chevron week," she said. "I've been sucking with the putter on the Chevron week, but it's not just me -- the greens were so tough that week.
"Here, hit it good and also making the putts. Also, got a lucky draw in the morning because it's not really windy in the morning."
Jeeno hit 11 of 14 fairways in regulation and 15 of 18 greens and needed just 26 putts after managing to adjust her mindset on the greens.
After the Chevron, she said, she went home and hit "a ton" of putts.
"I feel so good when I see it drop but I feel so bad when I see it miss," she said. "I was like, no, you can't be like this ... it's in or it's not, it has to be the same feelings and same emotion.
"If not, your emotion is going to be like rollercoaster for sure. I don't want to be so tight and tense," added the 22-year-old, who won her fourth and most recent LPGA title at last year's Tour Championship and won on Saudi Ladies International on the Ladies European Tour in February.
She had a two-stroke lead over two more morning starters -- France's Celine Boutier, South Korean Choi Hye-jin.
Boutier teed off on the 10th and after a bogey at 15 caught fire with a birdie at 18 that launched run of five straight birdies.
She added two more birdies at the sixth and seventh for her six-under 66.
"It was really nice to get going and get a few birdies in," Boutier said.
Choi had six birdies without a bogey in her 66.
Ryu Hae-ran, coming off a wire-to-wire victory in last week's Black Desert Championship, headlined a group of 10 players on five-under 67 that also included Germany's Esther Henseleit, American Jennifer Kupcho and Spain's Carlota Ciganda.
Ryu had six birdies in the first 10 holes, a bogey at the par-four 18th the only blemish on her card.
"I think the back nine started a little wind, it's hard to pick the club so I didn't have a lot of birdies there. But it's still good," Ryu said.
World number one and defending champion Nelly Korda had six birdies and two bogeys to lead another big group on four-under par 68.