Thailand's Jeeno Thitikul fired a four-under-par 68 to edge into a slender lead as searing heat and humidity tested players in the opening round of the KPMG US Women's PGA Championship in Texas on Thursday.
The 22-year-old, who is chasing her first major victory after seven top-10 finishes, reeled off six birdies to move into a one-shot lead.
Jeeno's only blemish on an otherwise flawless opening round was a double-bogey six at the par-four fourth hole of PGA Frisco's 6 404-yard Fields Ranch East layout.
The rising Thai star, who has already amassed 18 wins as a professional, including five on the LPGA Tour, said she had taken a patient approach after shrugging off her early double-bogey disappointment.
"I think, like all the majors, I have told myself just to be really patient," Jeeno said after her round. "I definitely know that I'm going to miss a shot or make a bogey during the day.
"Don't be like, moody... I told myself be patient and focused on the next shot."
Jeeno was one shot clear of Australia's Minjee Lee, who had a roller coaster round that included seven birdies and four bogeys en route to a three-under-par 69.
Lee was satisfied with her round but admitted the searing temperatures in the high 90s (Fahrenheit) were challenging.
"I just kept telling my caddie, can you give me another water, can you give me another water," Lee said. "I don't think we could have enough (water) out there. It's really hot."
Japan's Rio Takeda, South Korea's Lee So-mi and American Yealimi Noh were a further shot back after carding two-under-par 70s.
HEAT TAKES A TOLL
World No 1 Nelly Korda, meanwhile, is four off the pace after an opening level-par 72.
Korda also admitted she had found the heat a struggle.
"It's hot; I'm still cooling down right now," Korda said. "I'm pretty happy with my first round in the conditions.
"It definitely takes a toll on you, the Texas heat."
Auston Kim, who posted a one-under-par 71, said the heat had been more of a challenge than anything the twists and turns of the PGA Frisco layout had offered.
"I think the most difficult thing is dealing with the heat," Kim said.
"There were times I had to lock in really hard just because the heat is taking a toll on you. You kind of want to just get into a daze, and it's hard to focus.
"The heat was probably the hardest part, and then hitting the fairways. I had to chop it out of the rough twice today, including on the last hole.
"I thought I was going to make double for sure, but I managed to make a really good bogey."