Ko Jin-young responded to the loss of her world number one-ranking with an eight-under par 63 on Thursday for a one-shot lead in the LPGA Volunteers of America Classic in Texas.
An eagle and six birdies propelled Ko to the top of the leaderboard ahead of fellow South Koreans Lee6 Jeong-eun and Chun In-gee.
Ko topped the world rankings for 92 weeks before American Nelly Korda ascended to the top on Monday after capturing her first major title at the Women's PGA Championship last week.
"That's fine," Ko said of falling to second in the world. "And I’m still alive. So doesn't matter really."
Ko opened her round at The Colony near Dallas with seven pars then rolled in 15-foot eagle putt at the par-five 17th.
"I had a lot of birdie opportunities before the 17th but I didn't make any," Ko said. "I couldn't make any, and I don't know why.
"But then I made eagle at 17, so it was great momentum for me for the second nine," added the two-time major winner, who made six birdies in her last nine holes.
"Shot wasn't good, but putting was really good," Ko said. "And then I read the break really well today, so I had confidence on the green. I made a lot of putts today."
Chun and Lee6 both had seven birdies without a bogey in their seven-under 64s.
Lee6 capped her round with back-to-back birdies at 17 and 18 and Chun, who teed off on 10, finished strong with birdies at the sixth, seventh and eighth.
They were one stroke in front of South Korean Kim Min-G and American Emma Talley.
"I'm so happy to make bogey-free round today," said Chun, who wasn't sure that having a home in the area would actually be beneficial.
"Before the tournament I sleep at my house, so I feel like it's not a tournament week, so I was a little worried if I could make the good focus during the tournament.
"But I'm so glad I made a bogey-free round and a good score today."
She noted that the hot, humid weather was vastly different from the conditions players faced when they played the same course in December as part of the pandemic-disrupted 2020 season.
"But for me, hot weather is better than cold, so I can't complain," she said.