I know how to speak, read, and write Thai. First, I learned Loas but then I kept on watching Thai lakorns and had someone translate it for me (around the age of 10) so that's how I learned Thai. Because I already knew some Loas, it was pretty easy to learn and understand Thai.
My sisters can speak and understand Thai as well but they couldn't read so I taught them how to read, but they can't write yet.