During the filming, Jock Mahoney decided to show off his physical prowess by swimming across one of Thailand's biggest rivers. Co-star Woody Strode warned Mahoney that the river was one of the dirtiest, most polluted waterways in the world, but Mahoney wanted to save face and swam anyway. He made it, but contracted a severe case of amoebic dysentery and dengue fever, and finally pneumonia, going from 220 to 175 pounds before finishing the film. According to Strode (and to an interview Mahoney gave to Merv Griffin in the 1970s), it took him more than 18 months to recover and he was not the same man he was before. Though he continued acting, his physical stamina was dramatically decreased and he had to pass on many physical parts he might once have jumped at.
For his role as the dying ruler's evil brother, Woody Strode's voice was dubbed by British actor George Pastell.
Italian censorship visa # 41654 delivered on 9 November 1963.