T. S. Krishnan is an author, historian, and literary enthusiast who has conducted extensive research on South Indian temples, history, inscriptions, and literature. He has authored numerous articles and books in these fields, with particular focus on epigraphy and the copper-plate inscriptions of the various dynasties. His research engages closely with primary sources and inscriptional evidence, contributing to a deeper understanding of Indian political, religious, and cultural history.
He has authored books on the Cholas and the Gupta dynasty, and has compiled select inscriptions and copper plates of the Chera, Chola, Pandya, and Pallava kings. He has also written extensively on Vijayanagara and Tamil history, including the Madurai Nayakars, and is the author of Tamilnattu Porkalangal, which presents the history of Tamil Nadu through its major wars.
In the field of Tamil literature, T. S. Krishnan specializes in Sangam literature. He has also undertaken extensive research on classical Tamil epics including Silappadhikaram and Kamba Ramayanam. In addition, he translated the Sanskrit kavya Madura Vijayam by Gangadevi into Tamil, which narrates the liberation of Madurai by Kumara Kampanna of the Vijayanagara Empire. His translations further include notable scholarly works such as Arthaśāstra of Kautilya (by Thomas R. Trautmann) and Merchants of Tamilakam by Kanakalatha Mukund.