Tan Koon San was born in August 1944 in Bukit Mertajam, Penang, Malaysia. He graduated with a Bachelor of Arts (2nd Class Upper Hons.) degree in
History from the University of Malaya in 1967. Following a short period of teaching at the Phor Tay Girls High School, Penang, he entered the Diplomatic Service in September 1967. For the next twenty-nine years he served
in Tehran, London, Hanoi, Geneva, Warsaw
and Vienna, apart from intermittent home assignments. He was the Malaysian Ambassador to Austria and Permanent Representative to the International Atomic Energy Agency and the United Nations in Vienna before retiring in 1996.

He is a fifth generation descendant of a Chinese immigrant by paternal lineage and a third generation by maternal lineage. His paternal ancestor, his grandfather’s grandfather, migrated from Hai Deng 海 登 County, Fujian, China, first to Medan, Sumatra and then to Penang, during the Daoguang era (1820–1850) of the Qing Dynasty, following the aftermath of the First Opium War (1840–1842). There he laboured and sought new roots. The third generation, his grandson, then settled as a petty gentry planting rubber in the hinterland across Penang Island. The succeeding two generations served in the civil service.

His maternal grandfather migrated from Shantou, Guangdong Province, China, half a century later, in the dying days of the Qing Dynasty. He emigrated as a trader seeking opportunities in the thriving British Colony of Penang.

He published his first book Excellency - Journal of a Diplomat in 2000. This is his second book undertaken to trace the legacy of his ancestry and heritage.