Australian Brett Rumford raced into a three shot lead during the early stages of the Ballantine's Championship second round.
The three-time European Tour winner has been without a victory since 2007 but the 33 year old put himself in position with eight unanswered birdies in his first 14 holes.
That took him to nine under for the week with four to play - three clear of Wales' Rhys Davies, Dane Søren Kjeldsen and overnight leader Damien McGrane.
Former Trophée Hassan II winner Davies was the clubhouse leader after carding a second round 68, while Kjeldsen was five under for the day with three to play.
Ireland's McGrane was amongst the later starters at Blackstone GC in Icheon.
American Ryder Cup star Dustin Johnson was usefully placed on five under following a 69, alongside Park Sang-hyun and Richard Finch, who were both still to tee off - as was World Number One Lee Westwood.
