OSAKA  - Japan's Koki Kameda narrowly defeated Panomroonglek Kaiyanghadaogym of Thailand by a split decision to successfully defend his World Boxing Association (WBA) bantamweight title on Sunday.Two judges scored 115-113 and 115-114 in favour of the Japanese, who later apologised for what he said was a poor performance in the ring, while one judge counted it 116-113 for the Thai challenger. "I'm sorry," Kameda repeated six times during a short post-match interview. "It was not good at all...I'm very sorry for so many fans here."It was Kameda's sixth defence of the belt since winning the vacant title when he beat Alexander Munoz of Venezuela in December 2010. The victory sees him stretch his record to 30 wins, including 17 KOs, against one defeat. Panomroonglek, 29 and ranked eighth in the WBA, saw his record reduced to 36 wins, including 19 KOs, against two defeats. Kameda is part of a boxing family who have a bad-boy reputation. One of his brothers, Daiki, was suspended from boxing for a year after his failed title bid against then World Boxing Commission flyweight champion Daisuke Naito in October 2007 for using dirty tactics.Koki Kameda was reprimanded by the Japan Boxing Commission for urging Daiki to fight dirty. Their father, Shiro Kameda, has been barred by the WBC from serving as a cornerman in its matches for abusing officials. He has also been slapped with a life ban by Japan's boxing authority.