American Justin Thomas began his bid for a third CIMB Classic title with a six-under-par 66 to lie three shots behind first-round leader and compatriot Bronson Burgoon on Thursday. Thomas, the world number four who posted his first two career victories at the CIMB Classic in 2015 and 2016, birdied his last three holes to join 2012 champion Nick Watney, Briton Paul Casey and five others in a share of sixth place. Burgoon reeled off eight birdies and eagled the par-five 18th for a sizzling nine-under-par 63 to lie one shot ahead of American Austin Cook.