The 2018 Open Silver Medal winner carded a bogey-free seven-under-par 65 at the Ayrshire venue to lead by a shot at the halfway stage in the second event of the new season.
Locke, who is managed and mentored by the tour’s founder Paul Lawrie, had already made gains at the first and fifth before reeling off three birdies on the spin to finish the front nine.
He then picked up shots at the 12th and 16th coming home to earn a slender advantage over Ryan Campbell and Rory Smith.
Campbell, who also signed for a bogey-free effort, birded the first, seventh, 10th, 12th, 13th and 15th in an equally-impressive day’s work.
That also applied to Smith, who started birdie-bogey before covering the last 14 holes in six-under, including a hat-trick of birdies from the 11th.
Three players opened with five-under 67s, including Jack McDonald on his home course, with his effort being matched by Paul O’Hara, runner up in last week’s Montrose Links Masters, and Kieran Cantley.
Neil Fenwick, who topped last season’s money list, is within touching distance of the lead on 68, sitting alongside Challenge Tour winner Jamie McLeary, Scottish PGA champion Ross Cameron and Danny Kay in joint-seventh.
Former Scottish Amateur champion Michael Stewart was four-over after six holes before covering the remaining stretch in seven-under for a 69, turning his day around with an eagle-3 at the seventh.
Leader Locke also won the Scottish Amateur Championship, as did Chris Robb, who opened with a 69 as well and former South African Amateur winner Craig Ross, too.
Michele Thomson signed for three birdies in her 70, with 2005 Open Silver Medal winner also in a big group on that mark.
Gavin Hay, winner of the season-opener in Angus last Friday, opened with a 69, as did Sean Lawrie while his uncle Paul had to settle for a 74, the same score posted by Jack Doherty, who led after the first round in the season opener at Montrose Links.