Some people believe baptism can be accomplished by sprinking or pouring. Every Bible example of baptism involved believers. There is NOT one single Bible example of an infant being baptized. Nor is there a command to baptize infants. Infants are NOT born in sin.
Infants are too young to believe.
The important thing to note about the thief is that the New Testament was NOT yet in effect when he died on the cross. The thief on the cross lived and died under the Old Law - which did not require baptism.