Sure! Short of sending a letter to the church you were baptised at saying you're sorry but would they mind terribly much striking your name from the records, renouncing that religion altogether, you could just download a "de-baptism" certificate from the internet, sign it and get it witnessed.

What is the process of getting baptized?

In most cases, the parish priest or deacon administers the sacrament, anointing the person being baptized with oils, and pouring blessed water over the child or adult's head not just once but three times. ... Like the Sacrament of Confirmation and the Sacrament of Holy Orders, as a Catholic, you're baptized just once.

What are the three ways to get baptized?

Popularly, Christians administer baptism in one of three ways: immersion, aspersion or affusion.