Thongchai, on his fourth invitation to the elite Grand Slam event, finally made the halfway cut and played all the way to the end of the tournament. He is the first Thai to achieve that.
The ex-paratrooper from Lop Buri, who dreamed of professional glory while playing golf with tree branches as a youngster, played first and finished 55th among the top world golfers who managed to make the Masters cut last Friday night.
In doing that, he beat dozens of the top golf luminaries. They included such as Bernhard Langer, Jim Furyk, Padraig Harrington and Fred Couples, who was one of the favourites to win the year's first major event.
Thongchai finished in 55th place, and earned US$23,000 for the four-day tournament, just under B750,000.
And that ballyhooed battle of "Tiger versus Rory"? Really? Who cares aboutthose two guys?
As for the tournament winner, Spieth reached unprecedented territory at the Masters early Monday morning Thailand time.
With a birdie at the 15th hole, Spieth became the first player in Augusta National history to get to 19-under par.
That score didn't hold, as he finished with a bogey and fell to 18-under par, to win the tournament by four strokes.
He deftly handled the final-round tension to hold off Phil Mickelson and Justin Rose to win his first major title by four shots.
Writing an epic conclusion to a week of domination at Augusta National, the 21-year-old American fired a two-under par 70 to finish on 18-under 270, matching the 72-hole tournament record set by Tiger Woods in 1997.
"It's the most incredible week of my life," Spieth said. "It's a dream come true. I'm still kind of in shock a little bit."
Spieth claimed the green jacket symbolic of Masters supremacy and the top prize of $1.8 million at the $10 million event by denying two of golf's top major champions another crown.
"It was very nerve-wracking today," Spieth said. "With two major champions right behind me, I couldn't let up."
England's Rose, the 2013 US Open winner and Spieth's last-pair playing partner, shot 70 to share second on 274 with 44-year-old US left-hander Mickelson, a five-time major winner who shot 69.
"I played a good solid round but I needed something exceptional. I just didn't quite get it," Mickelson said. "I just got outplayed. Jordan played great."
Top-ranked Rory McIlroy, seeking a third consecutive major win to complete his career Grand Slam, was fourth on 276 after a 66, one stroke ahead of Japan's Hideki Matsuyama.
Woods, a 14-time major champion, fired a 73 to share 17th on 283, his best finish since 2013 and a sign that the worst of his physical and shotmaking woes might be behind him.
"Considering where I was... I'm really proud of it," Woods said of his effort.
Spieth was a runner-up to Bubba Watson last year in his Masters debut after squandering a front-nine lead on Sunday, but this time responded four times when dropping a shot to his rivals, restoring his margin each time on the very next hole.
"Every time I thought there was a chink in the armour, he would come up with a big putt," Rose said.
Spieth, who will jump from fourth to second in the world rankings, became the second-youngest winner in Masters history, five months older than Woods when he won his first major in 1997.
Also, Spieth became only the fifth wire-to-wire winner in Masters history, joining Craig Wood in 1941, Arnold Palmer in 1960, Jack Nicklaus in 1972 and Ray Floyd in 1976.
"It was awfully impressive," McIlroy said of Spieth's performance.
Starting with a four-stroke lead after setting the 36- and 54-hole Masters scoring records, the youngest 18-hole leader in Masters history answered every stumble quickly.
Three times on the front nine Rose trimmed Spieth's lead to three shots and each time the Texan boosted his edge back to four on the very next hole.
When Rose made bogey at nine and Spieth followed with a 23-foot birdie putt at 10, the lead was six shots over Rose and Mickelson.
Spieth's birdie at 10 was his 26th of the tournament, breaking the Masters mark of 25 set by Mickelson in 2001, and he added two more at the par-5 13th and 15th for good measure.
Spieth dropped a shot at the par-3 12th and Mickelson birdied the par-5 13th to pull within four. But Spieth birdied 13 to restore a five-shot edge.
Mickelson eagled the par-5 15th, blasting in from a greenside bunker, and Rose birdied 14 to join him on 14 under, both four back of Spieth with four to play.
Again Spieth responded. He went over the green at 15 but pitched to seven feet and made the birdie putt to reach 19 under par, the first time any player at any point in any Masters was so far below par.
Rose birdied to stay four back but he and Spieth parred 16 and 17 and made bogey on 18, Spieth missing a five-foot par putt at the last which would have given him the tournament record alone.
McIlroy went four under on the back nine to surge into fourth, his best Masters finish.
"I played well," McIlroy said. "I'm happy with how the weekend went. I'll take a lot of positives from it."
Woods missed every front-nine fairway and was favoring his right wrist after blasting an approach off pine straw and hitting a tree root at the ninth.
"A joint went out of place but I popped it back in," Woods said.
Woods showed at age 39 that he can contend in a major, although he said of his next start, "It's not going to be for a while."
Woods has not won the Masters since 2005, has not won a major since the 2008 US Open and has not won any tournament since the 2013 WGC event at Firestone. Bangkok Post/AFP