In the second half of the 2005–06 season, Kum replaced the injured Spira Grujić and made his debut for the club in a 2–0 loss against PSV Eindhoven on 29 January 2012 when he received a yellow card and played 90 minutes.

After two season with ADO at the league under manager John van den Brom, his career received an unexpected boost when Kum caught the attention of Kicker sports magazine's coverage of Germans playing abroad.

On 1 July 2012, Kum moved to SC Heerenveen on a free transfer under new manager Marco van Basten to the club defensive options and becoming the sixth summer signing.

Due to his good performance in the Jupiler League, Kum was pre-selected by Foppe de Haan for 2008 Beijing Olympic.

In his first training, ahead of a friendly match against Sweden, Kum made a good first impression but suffered an injury.