Career
He announced retirement in 2007 and in 2008 started to work with Fédération internationale de football association, first referee from Southeast Asia, as referee instructor. He was also the only non-African referee at the 2006 African Cup of Nations. In the 2010 World Cup at South Africa, Shamsul was appointed by Fédération internationale de football association to the referees committee.
He took charge of the group stage game between Trinidad and Tobago and Sweden, brandishing the first red card of the tournament to Trinidad and Tobago"s Avery John.
He also took charge of the group stage game between Mexico and Angola, sending off Angola"s André Macanga, becoming the first referee at the tournament to produce two red cards. By taking charge of the Mexico–Angola match, Shamsul also became the first Singaporean to referee more than one match at a World Cup Finals.
He was however not one of the 12 referees to officiate the quarter-final matches onwards as he was sent home along with 14 other referees despite giving one of the most consistent performances and escaping the scrutiny of the press which his fellow referees such as Valentin Ivanov and Graham Poll suffered from. The Australian media then blamed Shamsul for Australia"s defeat as he denied Australia a penalty after substitute striker Mark Viduka was allegedly brought down by Fabricio Coloccini.