John 6:29 Jesus answered and said unto them, This is the work of God, that ye believe on him whom he hath sent.
Didn't the thief have the work of God within him? I think it is plain that he believed that Jesus was the Christ.
Luke 23:42 And he said unto Jesus, Lord, remember me when thou comest into thy kingdom.
No, he didn't have time to grow and bear fruit for the Lord, but he did have the work of God within him.
I don't think we do any works of God through ourselves, it is only through the grace of God and him working within us.