Prammanasudh, coming off a victory two weeks ago in the Fields Open in Hawaii, had six birdies and a bogey on the Bosque Real Country Club course -- the longest on the tour at 6,932 yards and also the highest at about 8,000 feet above sea level.
'I'm still working on things,' Prammanasudh said. 'My swing doesn't feel completely perfect. I guess it never does. I'm just pleased to have played well today and hit some close shots to get some birdies out there.
'This is a completely different golf course than we've played previous weeks. You just have to try to play the golf course. There are some tricky holes out there and the elevation plays a big part in things. Picking the right club is definitely key.'
Play was suspended because of rain at about 3 p.m., then called for day because of darkness at about 6 p.m. Sixth-seven players were unable to complete the round.
Laura Davies and Marcy Hart opened with 68s, and Hee-Won Han and Christina Kim also were 4 under when play was stopped. Han had five holes left, and Kim had seven to go.
Sorenstam was another stroke back in a group at 69 that included Natalie Gulbis, while Mexican star Lorena Ochoa shot a 71.
Sorenstam has 69 career LPGA Tour victories, five in her first start of a season.
'I thought it was a good round considering it was my first competition of the season,' the Swedish star said. 'I had a good offseason where I had a chance to rest and a chance to practice, but you never know what it's going to be like to put a score together. As a matter of fact, I got to the first fairway and forgot my scorecard on the tee. It reminded that I was a little rusty.'
Ochoa, the tour's player of the year last season and also the AP Female Athlete of the Year, opened with a birdie, but dropped three strokes with bogeys on Nos. 2, 5 and 7. She rallied with birdies on Nos. 9, 12 and 15.
'I felt very confident,' Ochoa said. 'In the back, I had two birdies and managed to finish under par, not far from the leader. I am happy and positive.
'Today was a good day on the greens. It is the first day. I am more calm. I liked it a lot in the morning. The course is perfect. There was no wind. It was a good round. Tomorrow, I'll need another good score. I feel positive. I have a great support from the fans. I came here to enjoy the day.'
Paula Creamer, the winner of the season-opening SBS Open at Turtle Bay, shot a 75.