After the Resurrection, in the dispersal of the Apostles, the tradition is that St. Thomas travelled outside the Roman Empire to preach the Gospel, preaching the Gospel to the Parthians, Medes, and Persians. He ultimately reached India, where to this day there is a large native population calling themselves "Christians of St. Thomas." He is regarded as the Patron Saint of India, and the name Thomas remains quite popular in India.
Another ancient tradition was retained by the Guarani tribe in Paraguay. They say that St. Thomas visited them and converted them. Paraguayan miners once found some stones with ancient letters carved in them. Experts concluded that the letters carved in those stones were Hebrew-like symbols, but they couldn't translate them nor figure out the exact date when those letters were carved.
According to tradition, St.Thomas was killed in the year 72 AD, and his body was interred in Mylapore. Ephrem the Syrian states that the Apostle was martyred in India, and that some of his relics were taken then to Edessa. In the year 1258, some of the relics were brought to Abruzzo in Ortona, Italy, where they are kept in the Church of Saint Thomas the Apostle.
Marco Polo visited Southern India in 1288 and 1292. Where he met native Christians and recorded their tradition of Saint Thomas.