By Wanchai Rujawongsanti

Beijing - A reformed Manus Boonjumnong punched his way into history when he became Thailand’s first two-time Olympic medallist with his quarter-final triumph on Sunday night.

The defending light-welterweight boxing champion sealed a thrilling 7-5 victory over hot favourite Serik Sapiyev of Kazakhstan to reach the semi-finals and guarantee himself at least a bronze medal.

Manus' win has earned Thailand its 19th medal since the country first took part in the Olympics in 1952. He is the second Thai medallist in Beijing after weightlifting champion Prapawadee Jaroenrattanatarakoon.

"I am very happy," said the boxer from Ratchaburi. "It is like taking a mountain off my chest. He was the only boxer I was worried about."

Manus admitted he was exhausted after three rounds and needed encouragement from his cornermen to get to the final bell. The 28-year-old made a good start against the reigning world champion, leading 2-1 at the end of the first round.

Using hit-and-run tactics, Manus led 3-1 at the halfway stage. He added another point to lead 4-1 early in the third round, but then received a big scare.

His Kazakh rival received a huge boost when he scored one point and then two were deducted from the Thai's score for grabbing, after three warnings. That levelled the score at 4-4. The match hung in the balance at the end of the round, with the boxers alleven at 5-5 but Manus looking tired.

In the fourth and final round, Sapiyev, whom Manus defeated in the semi-finals of the 2006 Asian Games on his way to winning the gold, threw everything at the Thai, who scored a crucial point for a 6-5 lead early in the round.

Manus took the pressure off himself by landing a thunderous right with 30 seconds to go and then danced away from a frustrated Sapiyev. Manus collapsed in relief and lay face-down on the canvas after the final bell.

"I felt worried when I looked at my corner and was told that the score was level [in the third round]. I ran out of steam in the third round and had to grab my opponent to survive. At the end of the round, my cornermen had to encourage me to fight on," he said.

Manus made headlines after squandering millions of baht in bonuses he earned from his gold medal in Athens, reportedly on partying and gambling. After last night's historic win, he said he was now a changed man and thanked his fans and handlers for giving him a second chance.

In the semi-finals, he faces Roniel Iglesias Sotolongo of Cuba, who defeated Russia's Gennady Kovalev 5-2. Manus said he would give his all to win the bout as a present for his mother Malee, whose birthday falls on Aug 22, the date of Manus' silver medal match.

Athens bantamweight silver medallist Worapoj Petchkoom looks to join Manus as the next Thai to win more than one Olympic medal when he takes on Cuba's Yankiel Leon Alarcon in today's quarterfinals bracket.

Light-flyweight Amnat Ruenroeng and flyweight Somjit Jongjohor are the other two remaining Thai quarter-finalists.