Boi is another way to stylize the word “boy,” it has multiple usages.
According to Urban Dictionary, boi is a term used to make fun of someone when they do something stupid.
Boi can also be a queer-specific term. In the LGBTQ+ community, it is a way to describe someone who deviates from heteronormative gender roles. In lesbian communities, bois are often people who were assigned female at birth, but present themselves and act in ways traditionally associated with masculinity. The term originated in queer women of color communities.
Online, boi can be a replacement for any use of the word “boy.”