The 26-year-old fired an eight under par 64 and held an early four-stroke lead over a group which included last year's US Masters champion Charl Schwartzel.
Bremner was only a shot off the pace at halfway last December, but fell back to 20th with weekend rounds of 72 and 75.
"I played fantastically on the first nine - I could have shot 28," he told the Sunshine Tour website.
"I started thinking a bit more and playing clever golf as opposed to using too much aggression, which is what I normally do.
"It's got a lot to do with the work I've been putting in behind the scenes. I've been working with a sports psychologist and that's probably led to my change in thought patterns on the golf course.
"I can see the bigger picture now. It's not just about brawn - it's sometimes about the brain as well."
This time he did not look back after opening with two birdies. Four more followed for an outward 30 and he then made further gains at the 603-yard 11th and 628-yard 16th.
Schwartzel has still to win since his triumph at Augusta in April last year and has slipped from sixth to 33rd in the world in the past eight months.
He double-bogeyed the short 12th - his third of the day - but came back strongly to join compatriot Darren Fichardt, Swede Oscar Floren and German Bernd Ritthammer in second place.
England's Tommy Fleetwood, 124th on the European Tour money list and needing to move up five spots this week to keep his card, led when he turned in a four under 32, but in the end he had to be content with a two under 70, running up a seven on the long 16th.
Former world number one Martin Kaymer kicked off with a double bogey six on the 10th before recovering to match Fleetwood's 70.
Bremner's lead was trimmed to two by compatriot Matthew Carvell, who also had eight birdies but bogeyed the fifth and 15th.
Scotland's Craig Lee, at 116th on the European money list not yet safe for his card next season, moved into third place with an eventful 67.
It contained three bogeys, but also six birdies and an eagle two on the 382-yard second, his 11th of the day.
Branden Grace, hoping for a sixth win of the year, reached three under, but then double-bogeyed the short fifth and dropped another on the next before eventually signing for a level par 72.