He was runner-up in the World Junior Championships in 2000, defeated by Bao Chunlai in the final. He had good results in the Asian Badminton Championships, winning three titles. On 23 September 2007, Kuncoro won the Chinese Taipei Open Grand Prix Gold after beating Taufik Hidayat in the final round 18–21, 21–6, 21–13. He won the men's singles gold medal at the Southeast Asian Games in 2003 and 2005. At the SEA Games in 2007 and 2009, Sony helped the Indonesian team win gold in the men's team event.