J.S.
This may just be a stage and if it is... let him work through it. Don't make it a 'big deal' or he may grow to not liking baths at all. Honestly, with everything going around out there right now (especially Swine Flu) I say let him bathe 10 times a day if that's what makes him happy. If he continues to be like this for a year or more than MAYBE seek guidance from a professional. The only other thing I would work on is "time & place". Explain that he can take a bath, but some things come first; it will help with discipline and responsibility. It already sounds as if he has plenty of self-respect :)