Kingston, playing under preferred lies following heavy rain the previous day, enjoyed a bogey-free round with nine birdies en route to a record-matching score. But the South African thought he could have done better.
'I never thought I would sit here with a 61 and be disappointed about it,' said Kingston. 'Don't get me wrong. This was by far the best round of my life. It's the best round I've ever played from tee to green, and I've never had that many birdie opportunities.'
The 36-year-old, who's previous career-low on the Sunshine Tour was 64, had many chances to break the 60 mark, however he missed several birdie attempts including a 12-foot putt on the final hole of the Wild Coast course.
'I don't want to sound like I'm complaining about the course. The Wild Coast is my favorite course in the country, and I've always played well here,' said Kingston. 'But the greens have just got too much grass on them, and I would've loved to see the ball roll truer that it did.'
Kingston reconciled his emotions but still reflected on what could have been.
'I just feel that today was the day. If ever I was going to break 60, then it was going to be today,' he said.
He led at the halfway point of the South African Open a few weeks ago but relinquished the lead to eventual champion Tim Clark. This time he hopes to carry the momentum into the weekend on a quest for his third victory of the season.
'I'm playing well. I'm at ease with my swing and am hitting the ball consistently,' he said. 'When I make putts, I always score half decent. But I think I'm just in the frame of mind where I know I can win, and not just make cuts.'
The South African took the lead late in the round, overtaking his fellow countryman Moore (69) and England's Justin Rose (68).
Rose began the day two strokes off the lead but quickly jumped to 10-under with two birdies and an eagle over his first five holes. The 21-year-old ran into trouble on the par-4 15th, his sixth hole Friday, and dropped two of the shots he gained with a double-bogey.
The Dunhill Championship winner added another double-bogey on the par-4 2nd before making back-to-back birdies from the sixth to enter the clubhouse at 8-under 132.
The 21-year-old was joined by South Africa's Richard Sterne (66) and Scott Drummond (64) of Scotland.
The cut fell at one-over 141. Among those who missed the mark was Ireland's James Loughnane, a two-time winner of the Zambia Open.
Full-field scores from the Nashua Masters