The Gospel of Thomas is one of the Nag Hammadi (A complete version in Coptic (an Egyptian language derived from the Greek alphabet) was found at Nag Hammadi, Egypt in 1945. The complete text has been dated to about 340 AD, while some of the Greek fragments have been dated as far back as 140 AD) documents. It is not really a "Gospel" as we might expect, but, collection of random sayings attributed to Jesus. The author is unknown and since these sayings are not tied to historical events we cannot determine validity. There are also purported questions/statements from Simon Peter, Matthew, Thomas, and Mary.
Any of the discussions about this purported catalog of comments begin with disqualifiers such as:
How Many of the Sayings in the Gospel of Thomas come from Jesus? Who knows for sure?
Does the Gospel of Thomas reflect the views of Jesus? That is unclear.
Is the Gospel of Thomas Gnostic? It all depends on what you mean by Gnostic. Maybe.
When was the Gospel of Thomas written? This is a question hotly debated by scholars.
There are a couple things I would note. The Gospel of Thomas is very different in tone and structure from the four Canonical Gospels and even the NT apocrypha. It is not a narrative account of the life of Jesus; and while the text contains a possible allusion to the death of Jesus there is no mention of crucifixion, resurrection, or final judgment.
The Early Church believed it to be a false gospel. Eusebius, for example, included it among a group of books that he believed to be not only spurious, but "the fictions of heretics" that should be thrown out as absurd and impious.
The Gospel of St. Thomas is considered "Gnostic" in that it holds that salvation of the soul comes from a quasi-intuitive knowledge of the mysteries of the universe and of secret formula indicative of that knowledge.