RIO DE JANEIRO -- Inbee Park could tell right away Wednesday that this was not an ordinary golf tournament.
Walking onto the practice range, the South Korean flag on her red shirt and the Olympic rings just about everywhere she looked, the jangled nerves made her realize that playing in the Olympics -- the first for women's golf since 1900 -- brought the kind of pressure she doesn't usually feel.
On the golf course, Park was as unflappable as ever.
Facing top competition for the first time in two months, Park was flawless in a round of 5-under 66 that left her one shot behind Ariya Jutanugarn of Thailand.
Seiyoung Kim of South Korea also shot a 66.
"I was able to feel a lot of the players' nerves when I was on the range and when I was playing out there," Park said. "I haven't played in a while, but this is not what I usually get all the time. I was able to tell -- everybody was quite proud to represent their country and quite excited and quite nervous at the same time."
Jutanugarn, a four-time winner coming off her first major at the Women's British Open, kept her calm during a wild ride.
She pulled a 6-iron into the native area left of the green on the par-3 fourth hole and made double bogey, quickly erasing birdies on the previous two holes. Jutanugarn followed with another 6-iron to 8 feet for eagle on the next hole, and she was on her way.
"I had one double, but I felt OK," Jutanugarn said. "I want to play my game and not worry about it."
A short birdie putt on the 16th gave her a one-stroke lead after an opening round noted for the heat and laborious pace of play. It took the final threesome just over 5½ hours to complete the opening round.
For the second straight week, a Brazilian native opened the golf competition. Miriam Nagl was picked to hit the first tee shot.
"Being in my home country and golf being back in the Olympic Games ... it's just very special to me," she said. Nagl and Victoria Lovelady, the two Brazilians in the 60-player field, each shot 79.
Women's golf was last part of the Olympics in 1900 in Paris, and then it was only a nine-hole competition among 10 women.
These games are all about the South Koreans, who have dominated women's golf for the last generation. The maximum four players who qualified are among the top 10 in the women's world ranking, and there has been talk back home about sweeping the podium.
"Being a Korean women's golfer, I think we always have that kind of pressure on our shoulders," Park said. "It's hard, because we play 30 events a year, and there isn't many weeks where all Korean golfers finish 1, 2, 3. Being able to do it in the Olympics would be something unreal, but obviously it's going to be something that's very, very hard to do with all the great competitors around the world.
"At the same time, it is pressure for a lot of us," she said. "It is a really hard one. But you know, we really can't help it."
Spain got off to a strong start behind Carlota Ciganda (67) and Azahara Munoz (68), and Lexi Thompson led the three Americans at 68. Lydia Ko, the No. 1 player in women's golf, got into the picture only late in the day when she holed out with a 9-iron from 135 yards for eagle on the par-4 15th hole.
"It was my first eagle at the Olympics," Ko said after a 69. "So I think it's great."
Park, 27, last competed on a big stage two months ago at the KPMG Women's PGA Championship, where she became the youngest player to qualify for the LPGA Hall of Fame. Park missed the cut and skipped the next two majors because of a thumb injury that has been bothering her all year.
The time off allowed her to get ready for the Olympics. Park felt good in practice and carried that to the course, looking much like the player who has won seven majors.
Park never came seriously close to bogey. Her bid for a fourth straight birdie spun out on the 13th hole, and she missed a 6-footer on the next hole. Park missed six birdie chances from 10 feet or under, though that presented more hope than frustration.
"I always like to deal with missed opportunity than not even having an opportunity," she said.