Cue, but there are so many other scriptures that contradict what at first glance John 3:5 and Mark 16:16 seem to be saying, and we know that the bible doesn't contradict itself or we have bigger issues to deal with, so we must dig a little deeper and see how it all fits.
Salvation is either by grace alone through faith, or it's not. Physical baptism is something we go and physically do, so it would be a work. If that's required for salvation, then salvation is not by grace alone through faith but faith plus works.
Was the thief saved though? If yes, then how if baptism is a requirement of salvation and he wasn't baptized?