The Bible does not explicitly state where Thomas went after Jesus ascended to heaven. The Book of Acts tells us that after the ascension, the apostles, including Thomas, returned to Jerusalem and devoted themselves to prayer.
Church tradition and various apocryphal writings (which are not considered part of the biblical canon) suggest that Thomas eventually traveled east to preach the gospel, possibly to India. There is a community of Christians in India, known as the Saint Thomas Christians, who trace their origins back to the apostle Thomas.
However, it's important to remember that these are traditions and not explicitly stated in the Bible. The biblical account primarily focuses on the early church's activities in and around Jerusalem.