His particular area of knowledge centered on events in Java during the period, and he authored a number of works dealing with the subject.
Ong's family was upper-middle class, but through his maternal grandmother, Han Loen Nio, Ong hailed from the patrician Han family of Lasem, part of the baba bangsawan or the Chinese gentry of colonial Indonesia, and from a long line of Chinese officers who served in the civil bureaucracy in the Dutch East Indies.
In 1975, he received his Ph.D in History from Yale University with the dissertation The Residency of Madiun: Priyayi and Peasant in the Nineteenth Century.
He wrote a series of other books, mostly a collection of essays and articles, including Runtuhnya Hindia Belanda (The Fall of the Netherlands Indies), Negara dan Rakyat (The State and the People), and Dari Soal Priayi sampai Nyi Blorong—Refleksi Historis Nusantara (From Priayi to Nyi Blorong—Historical Reflections on the Indonesian Archipelago).
Ong Hok Ham, who was a Buddhist, suffered a stroke in 2001 and died six years later at Dharmais Cancer Hospital in West Jakarta at the age of 74.