A tall, heavyset attendant rang the gong at the start of Willie Scott's rendition of Anything Goes. Later, after Indiana Jones had been poisoned, Kao Kan appeared wielding a machine gun and the performer fled for his life as gunfire fired at Jones headed in his direction.
Behind the scenes
According to the article "50 Fascinating 'Facts' About Indiana Jones and the Temple of Doom" in Indiana Jones: The Official Magazine 3, Chief Guard actor Pat Roach played the role of the gong striker, as well as the Thuggee assassin in Pankot Palace. However, The Complete Making of Indiana Jones asserts that stuntman Bill Reed (who, like Roach, is listed in the film's credits) portrayed the gong striker, a role which has also been attributed in online discussion to Don Stansauk, though neither of these have been confirmed.
I asked Kathleen Kennedy about the gong ringer. She couldn't recall so she texted Frank Marshall. From the sound of it, Frank started digging. He thinks it's Stansauk. No definitive answer, but they all seemed to agree it wasn't Roach.
Frank said "Stansauk rings a bell (pun intended)"