Manus still in medal form

Manus, famous at home for his playboy antics, out-pointed the world light-welterweight champion in the quarter-finals to secure at least a bronze.

"It was really tough," the 28-year-old Manus (pictured here on the right) said after staying on course to become the first Thai boxer to win successive Olympic titles. "He was aggressive, always moving forward to attack. I was anxious."

The boxer rose to fame after Athens when, according to media reports, he squandered $600,000 worth of bonuses on women, gambling and drinking, prompting his pregnant wife to leave him.

After taking a break from the sport, he returned to the ring to win gold at the 2006 Asian Games in Doha, but made an early exit from last year's world championships in Chicago.

Thai amateur boxing president Taweep Jantararoj sent him to train in rural Vietnam without any money to ensure the country's best chance of an Olympic gold did not go off the rails.

It paid off on Sunday with a serious performance from Manus on his way to a 7-5 points decision.

A showman famous for holding his arms down to taunt his opponent, he kept his hands up this time, held his nerve and skilfully counter-punched.

Trailing 4-1 in the third round, the Kazakh fought back to level the bout at 5-5 entering the final round, during which two unanswered punches gave Manus victory.

"I got tired in the third round," Manus said. "During the rest time after round three, my coach said: 'You have to push yourself, because we have been waiting for this day'."

Manus will be tested when he meets Cuba's Rosniel Iglesias for a place in the final.

World welterweight champion Demetrius Andrade blamed the judges after sealing the U.S. team's worst ever Olympic boxing performance.

Andrade lost 11-9 to South Korea's Kim Jungjoo in his quarter-final bout, leaving the Americans with just one boxer, heavyweight Deontay Wilder, who struggled to beat Morocco's Mohammed Arjaoui on countback.

The situation is a major embarrassment for a country who have won a record 48 Olympic boxing golds and had never left Games with fewer than two medals.

"I was landing a lot of punches but the judges were not giving them to me," a distraught Andrade said. "It's tough for the kids back home who want to take up boxing because if they come to the Olympics to be treated like this, there's no point in coming at all," he added.