Kuchar stretched his lead up to 4-up following a 3-foot birdie putt at the eighth before seeing Kuchar battle back to within one with two holes to play.
Mahan, however, needed four shots to find the green at the par-4 17th and conceded the match to Kuchar.
Kuchar holds a 15-3 career record at this event, which is the highest winning percentage of anyone with at least 10 matches played.
Tiger Woods is the only player to successfully defend his title at this event, winning in 2003 and again in 2004.
The field consists of the top 64 players in last week's world rankings, but No. 1 Woods, No. 2 Adam Scott and No. 4 Phil Mickelson will not play this week, allowing Scott Piercy, Richard Sterne and Kiradech Aphibarnrat to take their place.
Humana Challenge winner Patrick Reed will be among the seventeen first-time participants this year.
Golf Channel will have television coverage Wednesday through Friday and early on the weekend before handing off to CBS in the afternoon.
The PGA moves east to Florida next week for the Honda Classic, where Michael Thompson picked up his first PGA Tour victory last season.
HONDA LPGA THAILAND, Siam Country Club, Chonburi, Thailand - The LPGA Tour is in Thailand this week for the Honda LPGA Thailand.
Inbee Park was surprisingly handed her first of six titles of the year at this event last season when Ariya Jutanugarn missed a 3-foot double-bogey putt at the 18th hole that would have forced a playoff.
The then-17-year-old Jutanugarn entered the tournament's final hole with a 2- stroke lead before seeing it slowly slip away.
Park will return to defend her title in her 2014 season debut against a field that includes the top 10 players in the world. With Park not participating in the first two events of the season, world No. 2 Suzann Pettersen and third- ranked Stacy Lewis have both pulled within 1.25 average points of Park.
Golf Channel will have mostly tape-delayed coverage this week.
The LPGA travels to Singapore next week for the HSBC Women's Champions, where Stacy Lewis earned a 1-stroke victory over Na Yeon Choi last year.