'When I was 5 under at the turn, I told myself `Just don't sit on it, you're playing well, keep doing what you're doing,'' said Prammanasudh, who matched the low round of her career.
Prammanasudh, who was part of the victorious United States team two weeks ago at the Solheim Cup, just missed an 8-foot birdie putt on the final hole at Capitol Hill's Senator Course.
'I thought it would move a hair right and it didn't,' she said.
Ochoa, coming off a monthlong vacation, was one under through her first eight holes, but she quickly shook off the rust to play the last 10 holes in five under par.
'I really didn't know where I would be after four weeks to get in competition again,' said Ochoa, who won the Women's British Open, Canadian Women's Open and Safeway Classic before her extended break. 'I'm really happy just the way I played today. Very solid and good rhythm, especially with my tee shots.
'No. 1, is just to enjoy the moment. Sometimes you try too hard, you don't play good. Other times it's just easy. It's one of those moments where I feel that everything is clicking in. I just feel comfortable out there and I like that. I'm going to try to repeat that as much as possible and enjoy the moment.'
Lindsey Wright and Virada Nirapathpongporn had 67s, while Nancy Scranton, who was seven under through 11 holes, double-bogeyed the final hole to join Danielle Downey at 68.
'The usual every week, 'Oh, there she is,'' Wright said of her reaction to seeing Ochoa back on the leaderboard. 'She's a great girl, a great player and that's what you expect from No. 1. She's awesome.'
Prammanasudh is looking forward to the challenge of trying to stop Ochoa's streak.
'There are three more rounds and anything can happen,' she said. 'I got off to a great start, but I've got to keep that going. There are plenty of great players out here that can win. The greens are pretty receptive and if they continue to be that way, then the scores should be relatively low.'