He expanded his business to all parts of Malaya, Thailand and India and diversified into insurance, paper and cement industries.

Tan was stripped of his Malayan citizenship in Singapore in 1963 by the Malaysian Federal Government as a suspected communist, and remained stateless since then.

As the long-time president of the Singapore Hokkien Huay Kuan, Tan Lark Sye contributed generously to charitable and educational causes throughout his life.

He donated S$5 million to its building fund, as well as 523 acres (2.12 km2) of land for its campus on behalf of the Hokkien Huay Kuan.

[9] On 19 October 2019, two parts of Nanyang Technological University (NTU) were re-named in honour of the pioneering contributions made by Tan Lark Sye and the Hokkien Huay Kuan to Singapore's education.

Nanyang Valley, a road in front of the Chinese Heritage Centre, was renamed the “Tan Lark Sye Walk”.