The only time I remember him entering the ring with a shaved head was for his return bout with George Foreman. He came into the ring with a hooded robe and when he took the robe off, the crowd reacted to his appearance. The feeling at the time was that it was to give him some sort of psychological edge over Foreman with a surprise change of appearance.
I remember that aha. It was actually the first time I ever saw Frazier as a kid watching YouTube and it felt weird not seeing him bald afterwards.
"Foreman doesn't recognize him as a threat through his disguise. Joe's creeping closer...closer...Foreman's just standing there, oblivious to the danger that the anonymous bald man poses...AND IT'S ALL OVER! ONE SURPRISE LEFT HOOK TO THE TEMPLE AND FOREMAN IS DOWN! THE COUNT IS AT EIGHT! NINE..."
Supposedly Joe got the urge to shave his head in the locker room, the inspiration came from his favorite tv show Kojak, starring Telly Savalas, who proved back in the hairy 70's that bald can be beautiful.