On 30 May, "Thompson" was reclassified as a fast minesweeper and given hull classification symbol DMS-38. She spent the month of June undergoing conversion for her new mission, commencing on 5 June. She completed her yard work on 29 June. During a post-conversion period, she conducted her first minesweeping exercises, with magnetic sweep equipment, in Chesapeake Bay. She also calibrated her radar, conducted antiaircraft exercises, and practiced laying mines. On 1 August, she departed the Virginia Capes and steamed toward the Panama Canal Zone, where she arrived on 7 August. While underway on 14 August, she received the news Japan had surrendered. On 18 August, she arrived at San Diego.