He was made to work extremely hard for it, though, by impressive young Australian Cameron John after a gripping final day duel on The Serapong at Sentosa Golf Club.

Ham closed with a three-under-par 68 to finish on 16-under and beat John by two shots. John shot a 66 while Spain’s Josele Ballester (66), Thailand’s Jazz Janewattananond (68) and Tomohiro Ishizaka (70) from Japan shared third, a distant seven behind the winner.

The result also secured Ham and John places in this summer’s Open Championship at Royal Birkdale, as the tournament is part of the Open Qualifying Series.

The Korean’s performance is one of the most impressive in the 57-year history of Singapore’s National Open, considering a place in the game’s oldest Major was on the line as well as valuable points on The International Series Rankings.

The weather also played a big part today, when, after three days of oppressive heat and humidity, the skies darkened, and at 11.47 am, play was stopped for just over three and a half hours due to lightning.

Ham started the day with a four-shot lead over John, and when the interruption occurred, they had completed seven holes with the Korean three ahead.

When play resumed at 3.30 pm, Ham picked up where he left off by holing a 10-foot putt for par on the eighth that helped settle the nerves and was typical of his performance on the putting surface all week. He had another testing four-footer for par on the next, which he slotted home.

It was then that John really put the pressure on with a succession of big birdie putts. The Australian holed a 25-footer for birdie on nine, meaning Ham was two ahead with nine to play.

Ham lipped out for birdie on the 10th before John closed the gap to one when he made a brilliant birdie on the 11th, draining a putt from 15 feet.

The 13th then produced high drama when Ham assumed the upper hand by holing his bunker shot for a birdie. It looked like he would move two ahead with John facing a 40-footer for birdie. To everyone’s astonishment, the Australian holed his putt to keep the pressure on his opponent.

The action continued at a pace when they both hit their tee shots close on the par-three 14th. Ham holed his from 12 feet before John followed him in from seven feet to keep the gap at one.

They both faced makeable birdie putts on the ensuing hole, but both missed, John first from 18 feet, then Ham from a slightly shorter range. On the par-three 17th again, they both missed makeable birdie putts, meaning Ham led by one with one to play.

On the par-five 18th, Ham sealed the deal when he reached the back of the green in two and two-putted for birdie, while John made par – although he nearly holed his chip from just off the green for a three.

Said Ham: “Honestly, I sweat a lot and struggle in the heat, so I just kept thinking: play quickly, get through it, and get back to the hotel as soon as possible.

“Of course, you still need to hit good shots, but because it was so hot, I actually wasn’t overthinking the golf too much. That probably helped me stay relaxed. I just wanted to finish quickly, shower, and lie down under the air-conditioning.”

Ham becomes the second Korean to win the event. Younghan Song was the first in 2016, beating then-world number one Jordan Spieth of the United States by one on The Serapong.

“My putting was really good today. I’d say the putter saved me for around six shots. Thankfully, the putter worked well and helped me keep the momentum going,” added the Korean.

It is the Korean’s first win on the Asian Tour, where he has only played 24 times since turning professional eight years ago, with 16 of those on home soil.

The impressive golfer’s textbook golf swing has previously brought him four wins on the Korean PGA Tour, the most recent being two years ago at the Golfzon-Toray Open.