"The story of Thomas’s Indian sojourn exists only in the Acts of Thomas. This long religious romance was probably written by the Syrian Gnostic poet Bardesanes about 210 CE at Edessa, Syria. Bardesanes was familiar with India and had met and discussed Indian philosophy with Buddhist monks travelling west to Alexandria. It was therefore quite natural for him to place his moral fable in India, a land from which all kinds of religious ideas emanated."
January 1, 1970
https://en.wikiquote.org/wiki/Acts_of_Thomas