Kim, who is nicknamed Tom due to his love of Thomas the Tank Engine as a child, started the week with a quadruple-bogey eight on his opening hole, but rebounded to shoot 67 and added rounds of 64, 68 and 61 to finish 20 under par at Sedgefield Country Club.
The 20-year-old - who is the second youngest winner on the PGA Tour since 1932 - made six birdies and an eagle in a front nine of 27 and although a bogey on the 10th halted his momentum, birdies on the 15th and 16th helped seal the victory.
Four players in the last 40 seasons - since hole-by-hole tracking began - made a quadruple bogey during a win on the PGA Tour. None had opened the tournament with one.
"I stayed very patient this week," Kim told CBS. "After that quad, once I started to laugh it off I was in a better mental state.
"Instead of getting angry and depressed I stayed in the moment and I can't believe I won with a quadruple bogey on the first hole. Hopefully that doesn't happen again but it's definitely a week that I will remember forever."
In his last TV commentary before retiring, six-time major winner Nick Faldo paid tribute to Kim, adding: "He's played brilliantly and I think there's something about him; that face, how relaxed he is.
"This is his first win on the PGA Tour, how special is this?
"He's handled everything so well, he's got some serious maturity. Looks like he's a fun lad as well, wants to enjoy himself and I've got a feeling we've just seen something very special."
Kim's win means he joins the PGA Tour as a full member and sees him added to the FedEx Cup standings in 34th place, bumping England's Matt Wallace from 125th to 126th and out of the play-offs by a single place.