Thonburi-class coastal defence ship

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HTMS Thonburi in Yokohama.jpg
HTMS Thonburi
Class overview
Builders: Kawasaki
Operators:Naval Ensign of Thailand.svg  Royal Thai Navy
Preceded by: Ratanakosidra class
Built: 1936–1938
In commission: 1938-1951
Completed: 2
Lost: 2
General characteristics [1]
Type: Coastal defence ship
Displacement: 2,265 long tons (2,301  t)
Length: 76.50 m (251 ft 0 in)
Beam: 14.43 m (47 ft 4 in)
Draught: 4.17 m (13 ft 8 in)
  • MAN diesels, 2 shafts
  • 3,900 kW (5,200 bhp)
Speed: 15.5  kn (17.8 mph; 28.7 km/h)
Complement: 155
  • Belt: 2 12 in (64 mm)
  • Turrets:4 in (100 mm)
  • Barbettes:4 in
  • Decks:1 12–1 in (38–25 mm)

The Thonburi class was a class of coastal defence ships of the Royal Thai Navy. It consisted of two ships built by Kawasaki and delivered in 1938, HTMS Thonburi and HTMS Sri Ayudhya.

Ship class group of ships of a similar design

A ship class is a group of ships of a similar design. This is distinct from a ship type, which might reflect a similarity of tonnage or intended use. For example, USS Carl Vinson is a nuclear aircraft carrier of the Nimitz class.

Coastal defence ship

Coastal defence ships were warships built for the purpose of coastal defence, mostly during the period from 1860 to 1920. They were small, often cruiser-sized warships that sacrificed speed and range for armour and armament. They were usually attractive to nations that either could not afford full-sized battleships or could be satisfied by specially designed shallow-draft vessels capable of littoral operations close to their own shores. The Nordic countries and Thailand found them particularly appropriate for their island-dotted coastal waters. Some vessels had limited blue-water capabilities; others operated in rivers.

Royal Thai Navy naval warfare branch of Thailands military

The Royal Thai Navy or RTN is the naval force of Thailand and part of the Royal Thai Armed Forces. It was established in the late-19th century. Similar to the organisational structure of the United States, the Royal Thai Navy includes the naval fleet and the Royal Thai Marine Corps. The Royal Thai Navy operates out of Sattahip Naval Base in Sattahip Bay. Thailand is the only Southeast Asian country that operates an aircraft carrier, though it is used as a pure helicopter carrier with the retirement of its Harrier fighter wing. Thailand was the second Asian nation to acquire submarines, following Japan, but has had no submarines since 1950.



Thonburi and her sister ship, Sri Ayudhya, were designed following the incorporation of the earlier Rattanakosindra-class gunboats into the Siamese Navy in the 1920s. The Ratanakosindra class were British-built ships which featured six-inch guns in two turrets and light armor. Under Plaek Pibulsonggram's command, the Siamese Navy began a series of modernization efforts. Priorities for the navy consisted of protecting the extensive Thai coastline, and coastal gunboats were viewed as the best resource. Several foreign firms from European countries offered a variety of designs, but in the end the Japanese company Kawasaki won the tender.

HTMS <i>Thonburi</i>

HTMS Thonburi, also known as Dhonburi, was a coastal defence ship of the Royal Thai Navy.

Sister ship

A sister ship is a ship of the same class or of virtually identical design to another ship. Such vessels share a nearly identical hull and superstructure layout, similar size, and roughly comparable features and equipment. They often share a common naming theme, either being named after the same type of thing or with some kind of alliteration. Often, sisters become more differentiated during their service as their equipment are separately altered.

HTMS <i>Sri Ayudhya</i>

HTMS Sri Ayudhya was a coastal defence ship of the Royal Thai Navy. It was in service from 1938 to 1951, being active during the Franco-Thai war in which its sister ship HTMS Thonburi was heavily damaged in the Battle of Ko Chang. Sri Ayudhya later served as flagship of the navy until it was sunk as a result of fighting in the Manhattan Rebellion.

The new vessels were basically larger versions of the earlier Ratanakosindra ships. The ships were laid down at Kawasaki's facilities in 1936, and the first, Sri Ayuthia, was launched on 21 July 1937. The resulting "battleships," as they were referred to in Siam at the time, displaced 2,265 tons, featured increased armor protection (protecting machinery and gun turrets), and were powered by twin diesels produced by MAN of Germany.

MAN SE German mechanical engineering company

MAN SE, formerly MAN AG, is a German mechanical engineering company and parent company of the MAN Group. It is a subsidiary of automaker Volkswagen AG. MAN SE is based in Munich. Its primary output is for the automotive industry, particularly heavy trucks. Further activities include the production of diesel engines for various applications, like marine propulsion, and also turbomachinery.


Armament consisted of four 8-inch (203 mm)/50 calibre guns mounted in pairs in two turrets. The Japanese 8-inch rifles were of the same type as mounted in early Imperial Japanese Navy heavy cruisers and the aircraft carriers Akagi and Kaga. The main armament had a maximum range of 24,000 metres (26,000 yd) at 25 degrees of elevation. A tower above the bridge featured a gun director for aiming the main guns. Additional armament consisted of four 3-inch and four 40-mm guns.

Imperial Japanese Navy Naval branch of the Empire of Japan

The Imperial Japanese Navy was the navy of the Empire of Japan from 1868 until 1945, when it was dissolved following Japan's surrender in World War II. The Japan Maritime Self-Defense Force (JMSDF) was formed after the dissolution of the IJN.

Japanese aircraft carrier <i>Akagi</i> aircraft carrier of the Imperial Japanese Navy

Akagi was an aircraft carrier built for the Imperial Japanese Navy (IJN), named after Mount Akagi in present-day Gunma Prefecture. Though she was laid down as an Amagi-class battlecruiser, Akagi was converted to an aircraft carrier while still under construction to comply with the terms of the Washington Naval Treaty. The ship was rebuilt from 1935 to 1938 with her original three flight decks consolidated into a single enlarged flight deck and an island superstructure. The second Japanese aircraft carrier to enter service, and the first large or "fleet" carrier, Akagi and the related Kaga figured prominently in the development of the IJN's new carrier striking force doctrine that grouped carriers together, concentrating their air power. This doctrine enabled Japan to attain its strategic goals during the early stages of the Pacific War from December 1941 until mid-1942.

Japanese aircraft carrier <i>Kaga</i> Tosa-class battleship converted to an aircraft carrier

Kaga (加賀) was an aircraft carrier built for the Imperial Japanese Navy (IJN) and was named after the former Kaga Province in present-day Ishikawa Prefecture. Originally intended to be one of two Tosa-class battleships, Kaga was converted under the terms of the Washington Naval Treaty to an aircraft carrier as the replacement for the battlecruiser Amagi, which had been damaged during the 1923 Great Kantō earthquake. Kaga was rebuilt in 1933–35, increasing her top speed, improving her exhaust systems, and adapting her flight decks to more modern, heavier aircraft.

Public opinion

The new ships were enthusiastically received by the Siamese Navy. Purchasing further vessels of the type was considered by the government, but ultimately it was decided to purchase two Italian-built cruisers in 1938. Both ships were seized by Italy in 1941 before construction had finished, leaving Thonburi and her sister ship as the most powerful combatants in Siamese service.


Ships in class

Ship nameCommissionedDecommissionedStruckFate
Thonburi 31 January 193826 September 194119 June 1959Severly damaged in the Battle of Koh Chang, 17 January 1941; Refitted and became training ship until being struck.
Sri Ayudhya 19 July 1938n/a8 October 1959Sunk during the Manhattan Rebellion, 1 July 1951.

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  1. Gardiner and Chesneau 1980, p. 410.


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