The submarines remained in service throughout World War II, which Thailand officially joined in January 1942, but they saw no combat. However, two of them did serve an unconventional role during the war. On 14 April 1945, five months before the Japanese surrender, Bangkok's Samsen and Wat Liab Power Plants were bombed during Allied air raids, leaving the capital city without electricity. In response to a request from the Bangkok Electricity Authority, the "Matchanu" and "Wirun" anchored at the Bangkok Dock Company and served as power generators for one of Bangkok's tram lines.