* CEO Elmer Funke Kupper's resignation is effective immediately
* Former employer Tabcorp probed by police over Cambodia plans (Adds quotes, Cambodia context)
SYDNEY, March 21 (Reuters) - Australian bourse operator ASX Ltd ASX.AX said its chief executive officer has quit to focus on unspecified potential investigations relating to his former role as head of gambling company Tabcorp Holdings Ltd TAH.AX .
Elmer Funke Kupper's resignation comes six days after Tabcorp said the Australian Federal Police (AFP) was investigating that company's activities when it was considering a move into the Cambodian sports-betting market in 2009.
Funke Kupper was CEO of Tabcorp from 2007 to 2011, before taking up his role at the ASX.
"The ASX board accepted that Elmer wanted to direct his full focus to the investigations which may be made into the Tabcorp matter, and not have them interfere with the important role of leading the ASX," ASX Chairman Rick Holliday-Smith said in a statement.
An ASX spokesman wouldn't comment further on the reasons for Funke Kupper's departure. The statement said the resignation would be effective immediately.
In an emailed statement, the AFP said it is investigating "allegations of foreign bribery relating to an Australian company, Tabcorp".
ASX is the world's eighth-largest exchange by free-float capitalisation, according to its website. ($1 = 1.3200 Australian dollars)