What navy used the ship "Prasae" in the Korean War?

The navy that used the ship Prasae during the Korean War was Thailand’s Royal Thai Navy.

Thailand joined the United Nations effort defending South Korea and sent naval vessels as well as army and air-force personnel. HTMS Prasae and her sister ship HTMS Bangpakong arrived in South Korea on November 7, 1950, and supported convoy escort and other maritime duties under the UN command structure.

The first HTMS Prasae had previously served as HMS Betony in the British Royal Navy and as HMIS Sind in the Royal Indian Navy. During a snowstorm on January 7, 1951, it ran aground near Yangyang on Korea’s east coast. Salvage attempts failed, and the vessel was eventually scuttled.

A later ship, often called HTMS Prasae II, also served with the Royal Thai Navy after transfer from the United States. That naming history can cause confusion, but the nationality answer remains Thailand: Prasae was operated by the Thai navy, not the British, Indian, or U.S. Navy, during the relevant Korean War service.