My opinion is that he is a very good boxer indeed, very wise fighter. The sad thing is that he couldn't speak simple English to express himself in his interview. As a balance, he should go back to college.
May be you are correct that he is professional in the sense that he is doing the kick and Muay Thai full time. Billy is most definitely a good Thai boxer and I know him personally.
For boxing, Billy has not been professional, probably not recognized by the relevant boxing associations. They have more rigid systems.