These verses are taken to mean that baptism is not essential for salvation, and that we go straight to Heaven at death. The thief was still living under the Law of Moses when Christ spoke to him.
True baptism is into the death and resurrection of Jesus.
Seeing that when Jesus spoke to the thief neither of those events had occurred, baptism into Christ was not possible. The thief was the only person who literally did this. It is quite possible that the thief was one of those who had been baptized by John the baptist. Likewise, the passage is silent about the words 'soul' and 'heaven'. 5. He knew that there would be a judgment day at the establishment of that Kingdom, and therefore he asked Jesus, whom he knew would rise from the dead to eventually be the judge on that day, to remember him for good.