Royal Thai Navy Submarine Memorial Day Date in the current year: September 4, 2024

The Royal Thai Navy was established in 1906 as the Royal Siamese Navy. The proposal to procure submarines was first voiced a mere four years later, but financial constraints limited the expansion of the Navy. It wasn’t until the 1930s that the budget of the Royal Siamese Navy allowed for such an expansion.

In 1934, Navy Chief of Staff Sindhu Kamalanavin presented a warship procurement project that included a budget for three submarines. The parliament approved the project in 1935, and the Royal Siamese Navy held a bidding that was won by Mitsubishi Heavy Industries, a Japanese company that offered to build four submarines for a price of 820,000 baht for each, which was well within the budget.

The submarines were built in Kobe while Siamese sailors and navy officers were undergoing training in submarine operation under the supervision of qualified Imperial Japanese Navy personnel. The first two submarines were delivered to the Royal Siamese Navy on September 4, 1937, the date that is now observed as Submarine Memorial Day by the Royal Thai Navy. The other two were delivered on April 30, 1938. All four submarines arrived in Siam on June 25, 1938 and were commissioned on July 19.

The Matchanu class submarines were relatively small, since their main task was coastal defense. Each had a displacement of 374.5 tons when surfaced and 430 tons when submerged, and was armed with four torpedo tubes, a deck gun and a machine gun. They only could submerge to a depth of 60 meters and required a crew of five officers and 28 sailors.

The submarines first participated in battle during the Franco-Thai War of 1940–1941. Following air raids on French military bases in Indochina carried out by the Royal Thai Air Force, the navy was mobilized to protect the territorial waters of Thailand, and the submarines were tasked with conducting reconnaissance. However, they failed to prevent a surprise French raid, which resulted in the Royal Thai Navy losing the Battle of Ko Chang in January 1941.

Despite remaining in service, the submarines saw no action during World War II. However, two of them were used as power generators for a tram line after Bangkok’s power plants had been bombed by the Allies, leaving Thailand’s capital with no electricity. After the war, the submarines couldn’t be used because the Allied occupation and disarmament of Japan cut off the only source of spare parts and supplies for the submarines.

After the failed Manhattan Rebellion attempted by a group of naval officers in 1951, the leadership of the Royal Thai Navy was fired, all naval combat aircraft and heavy weapons were confiscated, and the submarines were decommissioned.

Although the Royal Thai Navy has had no submarine force for decades, it still celebrates Submarine Memorial Day, honoring the people who used to serve in the force and hoping that one day the naval budget will allow to acquire new submarines.