His task could have been easier had he not three-putted the final green for just his second bogey of the week. Forsyth posted a 2-under-par 69 for a three-day total of 16-under 197, while Spain's Ignacio Garrido birdied two of the last four holes to move to 14-under with his second straight round of 67.
Stephen Leaney of Australia shot 66 for a share of third at 13-under with Spaniard Miguel Angel Martin, who carded an even-par 71. Sweden's Richard S. Johnson, a first-time winner last month at the ANZ Championship, climbed into contention again with a 66 for sole possession of fifth place at 12-under.
Garrido was active on the front side at Royal Selangor Golf Club, recording four birdies and two bogeys through the first seven holes to make the turn at 12-under-par. Forsyth, meanwhile, birdied both par-5s on the first nine -- the third and sixth holes -- before rolling in a six-foot birdie putt at the par-4 ninth to open a five-shot lead at 17-under.
Garrido, playing in the group in front of Forsyth, bogeyed the 11th hole to fall six strokes behind the leader. He rebounded with a birdie at the 12th, then added birdies at the 15th and 16th to cut Forsyth's advantage to three.
Forsyth failed to convert any birdie chances on the back nine, tallying pars on eight straight holes. He closed with a bogey after missing a four-footer to save par.
Full-field scores from the Malaysian Open