He is the identical twin brother of fellow referee Malcolm Changleng. Changleng began his rugby career as a player with Gala Reconstruction Finance Corporation, playing at fly-half in a team that included Gregor Townsend and Chris Paterson. Changleng has also been a regular referee in the Celtic League since its establishment in 2001-2002.
Early in his playing career, he also won one cap for the Scotland Under-21s. He became a regular referee in the Scottish Premiership and on the Borders Sevens Circuit, and refereed his first European game on 12 January 2002, when he officiated Montauban"s 40–9 win over Rovigo in the pool stage of the 2001-2002 European Challenge Cup. He took charge of his first Heineken Cup match three years later for the Leicester Tigers" 37–6 win over Calvisano in the pool stage of the 2004-2005 tournament.
