[3] The ban was later reduced to three months[4] to allow him to be involved competitively after his recent seven-week training stint with FC Nitra in Slovakia.
Zulkarnaen make his Singapore national team debut on 4 December 1995 during the 1995 SEA Games where he scores an equaliser in a 2–2 draw to Brunei at the Lamphun Province Stadium.
Zulkarnaen scored a late stoppage time goal in the 90+2 minute to equalise the game at 1–1 thus earning Singapore a point in the qualifiers.
Zulkarnaen was selected in the Singapore squad that won the 1998 AFF Championship where he scored a goal against Laos in a 4–1 win on 30 August 1998.
During the 2000 AFC Asian Cup qualification, Zulkarnaen scores the only goal in the match as he secures an important three points win over Macau on 16 February 2000.