On 23 September, she moved into the Gulf of Thailand near the west coast of South Vietnam to participate in one of the earliest naval gunfire support missions conducted along that section of the coastline. After a brief respite in Subic Bay for upkeep, the warship returned to the "gunline" in October, this time along South Vietnam's southeastern coast between Cape St. Jacques and Chu Lai. On 25 September, she provided call-fire for American and South Vietnamese forces operating ashore in the vicinity of Chu Lai itself. During the mission, her guns destroyed a number of enemy positions and figured prominently in the repulse of a Viet Cong attack. Near the conclusion of that 24-hour action, a 5-inch round misfired; and, during the ensuing efforts to clear the chamber, the shell detonated. The explosion damaged the gun mount, killed three sailors, and wounded three more. That event forced her departure from the combat zone. After landing the three casualties at Da Nang, "Turner Joy" set course for Subic Bay in the Philippines. After a week of repairs, the destroyer departed Subic Bay in company with "Ticonderoga" for screening duty in the South China Sea, followed by port calls at Hong Kong and at Yokosuka, Japan. At the end of the year, she returned to naval gunfire support duty off the coast of South Vietnam.