The 23-year-old American capitalised on overnight leader Anirban Lahiri's quadruple bogey nine on the par-five third hole to retake a lead he had held over the first two days before easing clear to win by three shots with a 23-under total.
"This is what you play for, to get into these situations and handle them well, like I did, and it's just a great start to the year," Thomas said in a greenside interview after sealing victory in the second event on the 2017 PGA Tour calendar.
Lahiri was searching for a maiden PGA Tour win at the TPC Kuala Lumpur course but the five-shot swing after he lodged his tee shot in a tree left the Indian with too much to do and he had to settle for a tie for third, four strokes back.
Japan's Hideki Matsuyama birdied the last two holes to sign for a 66 and claim second place on 20-under, with Lahiri (72) and American first round co-leader Derek Fathauer (67) rounding out the top four a further shot adrift.
After looking imperious in the first two rounds, Thomas suffered a mid-round meltdown on Saturday when he dropped four shots in three holes before a run of five consecutive birdies from the 14th kept him in touch with a surging Lahiri.
STRIKING DISTANCE
Thomas maintained his hot streak on Sunday with four birdies on his opening five holes to forge a two-shot lead over his faltering Indian playing partner and the American felt the closing stretch the previous day had set up his victory charge.
"I felt like maybe that was the biggest five holes I had played in my life because it gave me a chance," he added. "If I am going into today eight or nine back then I have no chance, so it gave me a lot of momentum and kept me in striking distance."
Thomas managed to keep his challengers at bay with some solid scrambling after the turn before an exquisite approach from 108 yards set up birdie on 16. He moved four clear of the field when he sank a monster putt on the next.
"I had little stretch there yesterday where I played pretty poorly but (caddy) Jimmy (Johnson) did an unbelievable job this week keeping me calm when it got tough ... I made some key up and downs on 12 and 13 and it feels great," Thomas added.
Australia's Marc Leishman fired a six-under 66 to finish alone in fifth place on 17-under, one ahead of American Keegan Bradley (68), who wilted on the back nine after climbing into contention going out.
The $7 million limited field event is co-sanctioned by the Asian Tour.
(Writing by John O'Brien in Singapore; Editing by Nick Mulvenney)
