The ship began taking part in the search from 6am Monday in the Straits of Malacca.
Navy chief Adm Narong Pipattanasai on Sunday instructed the Navy Operations Centre that HTMS Pattani, which is based in Phangnga, should join the search for the missing aircraft at the request of Malaysian authorities.
HTMS Pattani has 119 personnel on board, including 84 crew, nine Naval Special Warfare Command divers, three medics, 11 Super Lynx combat helicopter crew members, and 12 Dornier reconnaissance plane crew.
Rear Admiral Kan Dee-ubol, the navy secretary, earlier said the navies of Singapore and Vietnam were covering the search areas in Vietnamese waters and in the lower part of the Gulf of Thailand. The Thai navy is taking part in the search in the Straits of Malacca adjacent to the Andaman Sea.