Does this text teach that all the righteous dead will return with Christ at the end of the world? Who are these "saints" who will attend our Lord at His coming? By allowing the Bible to explain itself, every question is answered. Jesus described those who would come with Him in these words: "When the Son of man shall come in his glory, and all the holy angels with him, then shall he sit upon the throne of his glory." Matthew 25:31.
Please notice that Jesus said "all the holy angels with him" instead of "with all his saints," as Paul described it in this verse. Is there a contradiction? No. There is perfect harmony when we put all the texts together. Angels are actually called "saints" in the Bible. Moses described the giving of God's law on Mt. Sinai in Deuteronomy 33:2: "The Lord came from Sinai, and rose up from Seir unto them; he shined forth from mount Paran, and he came with ten thousands of saints: from his right hand went a fiery law for them."
Now compare these verses with Psalm 68:17: "The chariots of God are twenty thousand, even thousands of angels: the Lord is among them, as in Sinai, in the holy place." Here the thousands who attended God at Sinai are identified as angels, although they are called "saints" in Deuteronomy. In the same way, the saints who come with Jesus in 1 Thessalonians 3:13 are identified as angels by the Master Himself in Matthew 25:31.