Thomas was one of the twelve that had been with Jesus while he was here ministering in Judea. He was also called as Didymus (the twin) in John’s gospel.

He was the one who was ready to go with His Master to die with Him.

He said that unless Jesus told them plainly where He was going, they cannot know the way to that destination. This is when the Lord spoke the most quoted scripture about His identity and his uniqueness. I am the way, the truth, and the life: no man cometh unto the Father but by me. – John 14:6.
After the Lord’s death, Thomas was probably weakened in his faith. He was not with the other ten when Jesus appeared to them post His resurrection. Later when they told him about their meeting their Master alive and speaking, he was very candid in his remarks. Except I shall see in His hands the print of the nails and put my finger into the print of the nails, and thrust my hand into His side, I will not believe. – John 20:25.

And after eight days again His disciples were within, and Thomas with them: then came Jesus, the doors being shut, and stood in the midst, and said, Peace be unto you. Then saith He to Thomas, “Reach hither thy finger, and behold My hands; and reach hither thy hand and thrust it into My side: and be not faithless but believing”. And Thomas answered and said unto Him, “My Lord and my God”. Jesus saith unto him, Thomas, because thou hast seen Me, thou hast believed: blessed are they that have not seen, and yet have believed. – John 20:25-29. Thankfully, that includes us! Praise God!

Thomas was there when the Lord appeared to His disciples again for the third time at the sea of Tiberias. He was with the fishermen in the boat when the Lord said, “Cast the net on the right side of the ship and ye shall find”. And again, “Bring the fish that you have caught now”. The risen Christ not only cooked breakfast for them but also dined with them that morning. What a breakfast experience!

Thomas was in the upper room with the other disciples, Mary, the mother of Jesus and Jesus’ brothers (born to Mary and Joseph) – most probably James and Jude among others. He should also have been with them on that remarkable day of Pentecost – meaning the fiftieth day after the Passover – when the Holy Spirit descended upon them and took up residence permanently in the hearts of the believers – the day when the Church was born and His kingdom was established on this earth. Dr Luke does not specifically name the disciples that were assembled on that significant day though.

Thomas does not have a mention thereafter in the treatise that Dr. Luke wrote. But Thomas must have taken the Mandate of the Lord seriously. All power is given unto me in heaven and in earth. Go ye therefore, and teach all nations, baptizing them in the name of the Father, and of the Son, and of the Holy Ghost: Teaching them to observe all things whatsoever I have commanded you: and, lo, I am with you alway, even unto the end of the world. – Matt 28:18-20. Go ye into all the world and preach the gospel to every creature. – Mark 16:15. “Ye shall receive power, after that the Holy Ghost is come upon you: and ye shall be witnesses unto me both in Jerusalem, and in all Judaea, and in Samaria, and unto the uttermost part of the earth”. Acts 1:8.

Thomas is said to have reached Taxila in western Pakistan when Gondophares 1 (Kondaiappar?) was King. (Gaspar, as he was called in Persia / Armenia, might have been one of the few Magi who visited the young child Jesus in Bethlehem). Thomas preached the gospel of Jesus Christ and a few believed. He is also said to have built a palace for the King as Thomas was brought in from Syria by his minister Habban (Appan?).

http://www.indianchristianity.com/html/chap4/chapter4a.htm

He then landed in Muziris (Musiri was one of the busiest ports of the Chera Kingdom) or Thamizhagam in South India – today called as North Paravur and Kodungalur – in AD 50. He preached the gospel in Kerala and established “Seven room assemblies” (Ezharaipalli) churches for the converts who call themselves Saint Thomas Christians (Mar Thoma Nazranis) even today.

A Jewish community was already there at the time Thomas landed in India. [The Jews of India: A Story of Three Communities by Orpa Slapak. The Israel Museum, Jerusalem. 2003. p. 27. ISBN 965-278-179-7].
India during the time of Thomas (AD 52) had petty kingdoms ruled by small kings. They had trade relations with Asian and European traders who landed here to buy indigenous goods – pearls, muslin, ivory, diamond, spices, perfumes, and silk. –Barbara C Johnson, Cochin Jews of Kerala P27.

Some records say the first Jews sailed to South India on the ships of King Solomon; others say they came during the Babylonian Exile; others that they fled to Malabar after the destruction of the second temple. And others refer to a fourth-century migration from Majorca. Most of these stories revolve around the existence of a Jewish community in the ancient trade center of Cranganore / Kodungalur (Kodum Kolai ur) (which the Jews called Shingly – (river Changala a tributary of Periyar)), north of Cochin. One chronicle tells how a group of Jews descended from the Assyrian exile made their way to Calicut (further up the coast) by way of Yemen and a Malayalam Jewish song suggests that the Jews of the ancient town of Palur may have come from Yemen.

The theory that South Indian loan words appear in the Hebrew Bible (qapyim – apes/monkeys, thkyim – Peacocks (Thokai)) has been taken as evidence of commerce between the land of Israel and South India as early as the sixth century BCE and it is quite possible that there were Jews living in Cranganore during the period of extensive Roman trade around the beginning of the Christian era. It also seems likely that a community of Jews welcomed the first Christians who arrived in Cranganore as claimed in traditions linking these first Kerala Christians with the apostle St. Thomas. Early Christians from the middle east did tend to move to areas where Jews were already settled; there is evidence of a Syrian Christian community in Malabar as early as the third century and Hebrew signatures are found on a ninth-century Christian inscription in Kerala.