If you're already taking Muay Thai, you needn't much worry yourself with 'boxing' anyway.
In any case though, you can always train yourself with the help of visual aids off of the internet, in books, or on tape. But that's doesn't mean you'll be any good at all. How can you actually train yourself if you don't have any experience? If someone was teaching you any skill or trade, and they told you they had no experience in this, would you still be at all comfortable or faithful to their teaching? Doubtful.
Even if you had enough martial arts experience to train yourself for the most part, you're just not going to know the little details or tricks used in combat or in training by that art. If you "train yourself", you're never going to get the stuff that's passed down teacher to student.