Ong's wife Chan Choy Siong, a politician and women's rights activist, died in a car accident in 1981, leaving behind her husband and their three children.
[3] In 1955, Ong's foray into politics began as a polling agent for Lee Kuan Yew in the 1955 legislative assembly election.
He held the post until he resigned in April 1959 to contest the Legislative Assembly election as the PAP's candidate for Telok Ayer.
He was subsequently appointed as Minister for Home Affairs in the first self-government Cabinet and played a key role to eradicating yellow culture and crime in Singapore society.
By increasing the teaching of English in Chinese schools and vice versa, he was instrumental in laying the foundation for the bilingual policy for which Singapore is famous.