The thief could never be with Jesus bodily because flesh and blood cannot inherit the Kingdom. 1 Corinthians 15:50. Here we have Jesus just about to enter into the realms of death and hell. Prior to the cross, mankind were destined to the penalty of sin which is death Romans 5:12, Romans 6:23, Romans 7:5, and would enter into the very place Christ had entered. However, Christ conquered death when God raised him up. Hebrews 2:14. This automatically took the power of death and hell out of the enemies hands. Revelation 1:18.
Getting back to the thief on the cross ~ Luke 23
40 But the other, answering, rebuked him, saying, “Do you not even fear God, seeing you are under the same condemnation? 41 And we indeed justly, for we receive the due reward of our deeds; but this Man has done nothing wrong.” 42 Then he said to Jesus, “Lord, remember me when You come into Your kingdom.”
43 And Jesus said to him, “Assuredly, I say to you, today you will be with Me in Paradise.”
I believe that Jesus was speaking figuratively as one who enters into his rest.
Therefore, while the promise to enter His rest remains, let us fear that none of you should miss it.2 For we also have received the good news just as they did; but the message they heard did not benefit them, since they were not united with those who heard it in faith 3 (for we who have believed enter the rest), in keeping with what He has said: So I swore in My anger, they will not enter My rest.
And yet His works have been finished since the foundation of the world, 4 for somewhere He has spoken about the seventh day in this way:
And on the seventh day God rested from all His works.
5 Again, in that passage He says, They will never enter My rest. 6 Since it remains for some to enter it, and those who formerly received the good news did not enter because of disobedience, 7 again, He specifies a certain day—today—speaking through David after such a long time, as previously stated:
Today, if you hear His voice,
do not harden your hearts.
8 For if Joshua had given them rest, God would not have spoken later about another day. 9 Therefore, a Sabbath rest remains for God’s people. 10 For the person who has entered His rest has rested from his own works, just as God did from His. 11 Let us then make every effort to enter that rest, so that no one will fall into the same pattern of disobedience.