[3] Ong signed for S.League Champions Warriors FC for the 2015 S.League season after failing to make any appearances for the LionsXII in the 2014 Malaysian Super League.
However, things took a turn when Ong was given a run out in their 2-0 loss to Maldivian side Maziya FC and impressed coach Alex Weaver.
Ong began to hold down a starting role in the team and kept experienced and foreign players such as Shi Jiayi and Thomas Beattie out of the side.
[9] Although he was just a backup player in the LionsXII squad, Ong was called up to the Singapore Under-21 team for the Hassanal Bolkiah Trophy, one of the much-respected Southeast Asian youth tournaments.
[10] In 2017, Ong was called up to the national team for the friendly against Hong Kong and the 2019 Asian Cup Qualifiers against Turkmenistan on 31 August and 5 September respectively.