Sadom, the joint-overnight leader, fired a composed bogey-free 69 on the Serapong Course to finish on 13 under and beat Japan’s Yuto Katsuragawa and Joohyung Kim from Korea by three strokes.
Katsuragawa returned a 68 while Kim wrapped up the Asian Tour Order of Merit title after signing for 69.
Sihwan Kim, who started the day sharing the lead, carded a 73 to take fourth place.
All four players booked their tickets to this year’s Open Championship at St Andrews as this week’s event is part of the Open Qualifying Series.
Sadom produced another inspired level of golf today that confirmed his status as one of hottest young golfers in the region and a star of the future.
The 23-year-old was never really challenged on an extremely hot day. After Sihwan Kim made bogey on the first Sadom took the outright lead and did not look back. Birdies on six and seven saw him move three ahead and he calmly parred his way home and enjoyed the comfort of a three-shot lead playing 18.
He picked up a cheque for US$225,000 and finished the year in second place on the Merit list, with US$378,972.
The victory continued Sadom’s remarkable recent run of form: in the final three months of last year, he won five times in Thailand, including the Thailand Open.
He’s won once before on the Asian Tour, at the 2019 Bangabandhu Cup Golf Open – which saw him become the fastest Qualifying School graduate to win on Tour as it was his first start after graduating.
“This is amazing, it wasn’t easy,” said Sadom, who was also bogey free on Saturday.
“It has taken a lot of hard work to get here, especially over the last two years. This is a great way to start the year. I hope it’s the start of a great year.”
Joohyung Kim, aged 19, fought hard to catch him but it was not to be his day.
He said: "Just trying to grind it out. It’s too bad, I felt like I had a shot, but obviously I couldn’t be so aggressive because just knowing that I had The Open on the line as well. I just tried to play through my game and I felt like I didn’t have my 100% today and it’s pretty disappointing. But we learn, and hopefully just come back stronger."
He becomes the second youngest winner of the coveted Merit title after compatriot Seungyul Noh – who was also 19 when he won in 2010 but he is a month younger.
The tournament’s star player, Paul Casey from England produced his best performance of the week by shooting 66 to tie for 16th, while Thailand’s 14-year-old amateur sensation Ratchanon Chantananuwat closed with a 71 to finish equal 34th.
Koh Dengshan ended as the leading Singaporean after coming in with a 73 to tie 60th.
By being the top local player, he booked his place in the field for next month’s PIF Saudi International powered by SoftBank Investment Advisers.
The Asian Tour commences its 2022 season at the US$5 million Saudi event, which will be played at Royal Greens Golf and Country Club from February 3-6.
The top-30 players from today’s final Merit list have qualified for the event.
Scores after round 4 of the SMBC Singapore Open being played at the par 71, 7411 Yards Sentosa GC course (am - denotes amateur):
271 - Sadom Kaewkanjana (THA) 67-70-65-69.
274 - Yuto Katsuragawa (JPN) 68-70-68-68, Joohyung Kim (KOR) 68-68-69-69.
275 - Sihwan Kim (USA) 67-66-69-73.
277 - Doyeob Mun (KOR) 70-70-71-66, Jarin Todd (USA) 71-72-68-66, Veer Ahlawat (IND) 68-70-70-69.
278 - Ben Campbell (NZL) 70-70-69-69.
279 - Shintaro Kobayashi (JPN) 69-70-73-67, Kosuke Hamamoto (THA) 68-71-71-69, Shiv Kapur (IND) 71-69-70-69, Bio Kim (KOR) 71-70-66-72, Zach Murray (AUS) 68-73-65-73.
280 - Ben Leong (MAS) 71-73-67-69, Justin De Los Santos (PHI) 67-71-68-74.
281 - Paul Casey (ENG) 76-68-71-66, Dongkyu Jang (KOR) 68-69-73-71, Matthew Griffin (AUS) 71-69-70-71, Suradit Yongcharoenchai (THA) 66-73-70-72, Richard T. Lee (CAN) 73-66-70-72, Travis Smyth (AUS) 72-70-67-72, Steve Lewton (ENG) 68-74-65-74.
282 - Panuphol Pittayarat (THA) 71-72-71-68, Prom Meesawat (THA) 73-71-69-69, Siddikur Rahman (BAN) 70-71-71-70, Shunya Takeyasu (JPN) 69-73-69-71, Chen Guxin (CHN) 72-70-69-71, Jake Higginbottom (AUS) 71-71-68-72, Taehoon Ok (KOR) 66-72-71-73, Phachara Khongwatmai (THA) 70-71-68-73, Genki Okada (JPN) 70-69-69-74.
284 - Itthipat Buranatanyarat (THA) 70-71-73-70, Hongtaek Kim (KOR) 71-73-71-69.
285 - Ratchanon Chantananuwat (am, THA) 68-74-72-71, Hein Sithu (MYN) 69-74-71-71, Konosuke Nakazato (JPN) 74-71-68-72, Trevor Simsby (USA) 71-70-72-72, Pavit Tangkamolprasert (THA) 75-70-70-70, Paul Peterson (USA) 70-74-73-68.
286 - Kaito Onishi (JPN) 69-71-74-72, Danthai Boonma (THA) 69-72-70-75, Seung Park (KOR) 71-73-72-70.
287 - Tirawat Kaewsiribandit (THA) 68-76-70-73, Sungyeol Kwon (KOR) 69-70-74-74, Berry Henson (USA) 71-74-69-73, Jeongwoo Ham (KOR) 73-71-71-72, Masanori Kobayashi (JPN) 69-73-67-78.
288 - Eunshin Park (KOR) 71-73-70-74, Chang Wei-lun (TPE) 69-74-71-74, Seungsu Han (USA) 69-74-72-73, Viraj Madappa (IND) 71-69-75-73, Todd Sinnott (AUS) 75-68-73-72.
289 - Charlie Wi (KOR) 74-70-70-75, Natipong Srithong (THA) 71-73-71-74, Rashid Khan (IND) 72-73-71-73, Poom Saksansin (THA) 71-73-74-71.
290 - Christoffer Baumann (SWE) 76-69-71-74, Yuki Shino (JPN) 74-69-76-71, Janne Kaske (FIN) 73-66-68-83.
291 - Bjorn Hellgren (SWE) 70-72-70-79, Ryoma Iwai (JPN) 74-71-71-75, Yosuke Asaji (JPN) 78-67-72-74, Koh Deng Shan (SIN) 69-76-73-73, Daniel Fox (AUS) 73-72-74-72.
292 - S. Chikkarangappa (IND) 73-71-72-76, Gunn Charoenkul (THA) 71-71-77-73.
293 - Yuwa Kosaihira (JPN) 69-75-72-77, Jack Harrison (ENG) 73-71-74-75, Miguel Carballo (ARG) 72-73-74-74.
294 - Angelo Que (PHI) 72-68-75-79.
297 - Danny Chia (MAS) 71-73-74-79, Mitchell Slorach (SIN) 75-69-74-79, Nicholas Fung (MAS) 73-72-75-77.
299 - Nicklaus Chiam (SIN) 69-75-78-77.