As asides, the church in India looks to the Apostle Thomas as its founder. There are--go figure--two Thomas tombs in India. Eusebius places him in Parthia, Jerome in Persia, all points east of Jerusalem.
And a non-canonical Gospel bears his name, the Gospel of Thomas. This short and choppy work has many parallels to the canonical Gospels (Matthew, Mark, Luke, and John), but also some odd additions especially at the beginning, at least one of which may have placed it in the so-called Nag Hammadi library, which set of ancient documents (in Egypt) stems from a syncretistic religion (partly borrowing from Christianity, partly from other religions) called Gnosticism--also condemned by church father Ireneaus. The Gospel of Thomas contains no record of Jesus' death and resurrection.
In this life, we may never know quite how the text of the Gospel of Thomas we have came about (possibly in Syria), but I am partial to the notion that Thomas himself evangelized India (in apparently non-Gnostic fashion) in keeping with Jesus' Great Commission of Matthew 28 (cf. Acts 1:8). God Has His believers in places "to the ends of the earth."