folks who suggest that the repentant theif died under the new covenant and hence needed to baptize and beleive.
The thief did die under the New Testament and his faith in Christ saved him.
The issue in Mark 16 isn't the Baptism, it is the believing, since what is repeated in the second part of the verse is 'and he that believeth not is condemned'
Moreover, Christ gave that command after His Resurrection, so the Baptism is referring to the spiritual baptism of 1Cor.12:13, not water baptism.