His family migrated to Malaya (present-day Malaysia) when the Japanese started attacking coastal China.

He spent his childhood in Taiping, Perak and attended Chung Ling High School and Nanyang University.

[1][2] Chai had originally wanted to contest in the 1968 general election but was not able to due to having gotten his Singaporean citizenship in 1967, too late to place himself on the electoral register.

[6] Chai contested at the 1976 general election for MP representing Bukit Batok SMC against Sulaiman bin Jaffar of Singapore Justice Party.

[11] At the 1984 general elections, he contested for MP of Bukit Batok SMC again, against Tan Jue Kit of United People's Front.

[16][2] While he worked at Shell, he met his future wife Khor Phaik Tin, who studied at Teacher's College in Kuala Lumpur.