Ong enlisted in the Singapore Armed Forces (SAF) in January 1994 and was commissioned as an infantry officer in October that year.
Ong has held various appointments in the SAF, including the Commander of the 7th Singapore Infantry Brigade from 2010 to 2011, and Head of the Joint Plans and Transformation Department.
In 2011, Ong led the Singapore team which assisted in rescue operations and provided humanitarian aid to the victims of the 2011 Christchurch earthquake in New Zealand, and helped to establish the Changi Regional Humanitarian Assistance and Disaster Relief Coordination Centre in 2014.[3] He was also Chairman of the 2015 National Day Parade Executive Committee.[2]
Ong served as Chief Guards Officer from 18 June 2014 to 14 August 2015.[4] He succeeded Perry Lim as Chief of Army on 14 August 2015,[2][5] and was promoted to the rank of Major-General on 1 July 2016.[6] He served in that position until 21 March 2018.
Ong was appointed Chief of Defence Force on 23 March 2018,[7] and was promoted to the rank of Lieutenant-General on 1 July 2018.[8] He served in that position until 24 March 2023, where he was succeeded by Aaron Beng.
Non-military career
In addition to his career in the SAF, Ong is also serving in the Singapore Administrative Service under the Dual Career Scheme. He was Deputy Chief Executive Officer of the Early Childhood Development Agency between 2013 and 2014.[4]
He became the Permanent Secretary for Defence Development at the Ministry of Defence on 1 June 2023, succeeding Chan Heng Kee.[9] On 1 January 2024, he had also assumed the role of Permanent Secretary (Development) at the Ministry of National Development.[10]