Scripture is silent on the issue so one cannot presume that the thief who was being executed for crimes had done enough good works to merit heaven.
Then there's this account....
Luke 18 9He also told this parable to some who trusted in themselves that they were righteous, and treated others with contempt: 10"Two men went up into the temple to pray, one a Pharisee and the other a tax collector. 11The Pharisee, standing by himself, prayed thus: 'God, I thank you that I am not like other men, extortioners, unjust, adulterers, or even like this tax collector. 12 I fast twice a week; I give tithes of all that I get.' 13But the tax collector, standing far off, would not even lift up his eyes to heaven, but beat his breast, saying, 'God, be merciful to me, a sinner!' 14I tell you, this man went down to his house justified, rather than the other. For everyone who exalts himself will be humbled, but the one who humbles himself will be exalted."
Neither can u prove that he was saved by his faith only. You know nothing about the thief and neither do I. He may of been baptized by John the Baptitst, we just don’t know. He may have been baptized by one of John’s followers, we just don’t know.
I can’t make assumptions about the thief and neither can u. We only know what the Bible teaches.
James 2:24
You see then that a man is justified by works, and not by faith only.
The thief did let us know he "deserved" the punishment given which of course evidenced whatever he did, in his eyes, he was guilty of...and clearly theft was mentioned.