Smith's form was scratchy coming into the PGA Tour event in Kuala Lumpur, having missed the cut in seven of his last 10 outings, but he ripped up the course on day one to move into first place.
The Australian made eight birdies in a bogey-free display to move into early contention for a second title on the American circuit, having broken his duck at the Zurich Classic of New Orleans back in May.
Poom Saksansin of Thailand is in a three-way share of second on -7 alongside American pair Keegan Bradley and Xander Schauffele, who has continued his impressive form from the runners-up finish at the Tour Championship.
Kevin Na, Gary Woodland and Pat Perez are a further stoke back after shooting rounds of 66, while there is a group of six players sitting on -5, just three shots off the pace in the early stages.
South Korean Sung Kang, Spaniard Rafa Cabrera-Bello, India's Anirban Lahiri, Thailand's Phachara Khongwatmai and the American pair of Brendan Steele and Davis Love III all signed for rounds of 67.
Defending champions Justin Thomas, who is aiming to become the first player to win the tournament three times in a row, opened with a steady two-under-par 70.