The idea of this part of my Alternate Universe come from a drawing found on the website "combined fleet"(
http://www.combinedfleet.com/furashita/thombu_f.htm).
While the design of the ship is quite close, his history is slightly different:
After the end of first world war the disarmement of the defeated central powers and the treaty limiting the strenght of the winners, gave to smaller naval powers the opportunity of increasing there fleet in a very economic way.
Siam was one of the nations that seized this opportunity by acquiring in 1924 the japanese battleship Satsuma that was to be scrapped to comply with the provisions of the 1922 Washington treaty.The ship was renamed Abhakara Kiartivongse, in reference to the Admiral prince, "The Father of Royal Thai Navy".
The french felt they have to increase their strenght in the area to counter that new threat. So Admiral Teston d'Aigues-Vives, the newly appointed commander of the french far-east Naval Forces , obtained the battleships Diderot and Voltaire of the Danton class to be assigned to his squadron in 1925 and 1926.
This tiny naval arms race was suspended until the thailand navy send his ship back to japan to be modernised in 1930. The ship was commissioned in 1934. His gun firepower was reduced by downsizing from 254mm to 140mm, even if the main gun were rebored to 320mm.8 torpedo tubes were added. The speed was increased to 26 knots by removing the old 17,300 shp engines and installing a brand new 102,000 shp group. A massive superstructure inspired by the heavy cruiser takao was installed. Surprisingly ,no seaplane lauching capability were instaled.
The french central governement didn't felt the need to follow on as they had a numerical advantage with two battleship. But Teston d'Aigues-vives was concerned by the growing ambitions of japan in the area, and feared to fight on two fronts. Initialy formed as naval architect he set up a work group with local engineers to design a reconstruction program for the ships. He used his contact to acquire some informations and plans about the Dunkerque battlecruisers that were under construction. This way he was able to use a maximum of parts already designed and produced to lower the cost of the program and make it enough affordable to be accepted. Finally a subscription of the local french settlers were necessary to fund a part of the program and the Diderot was the first to sail back to french shipyards in 1933. The two ships were in active service by 1938. The new 84,000 shp engine gave a top speed of 24 knots. The six twin 240mm turrets were replaced by two dual purpose quadruple 130mm turrets. No torpedo tube were added but each ship carried four loire 130 seaplane with two catapults. To end the transformation a massive fore control tower was fitted in the dunkerque class style.
As thai admiralty finally realised they missed aerial spotting capability for their battleship, two old mutsuki class destroyer were bought in 1936 to be converted to small aircraft cruiser. Each were armed with a twin 140mm turret ( same as the secondary armement of their admiral ship) and carried two seaplane. Those ships formed the Thao Suranari Class (second ship was named Sing Singhaseni) and were commissioned in 1938.
The Diderot participated in the Battle of Koh Chang on the french side (as Voltaire was anchored in Haïphong) the Abhakara Kiartivongse and the Sing Singhaseni on the thai side. The thai battle ship sunk in shallow waters and was later raised and send for repair in japan, is smaller fellow was destroyed by an internal explosion (probably due to airplane fuel tank).
The Abhakara Kiartivongse was on his way back to homeland under escort of lady Mo (Thao Suranari nickname) and japanese ships when the Prime Minister Phibun was forced from office in June 1944. The japaneses ordered to seize the thai ships and later used them in the Japanese coup of March 1945 against the french indochina.
As Admiral Teston d'Aigues-Vives refused to destroy his fleet as in Toulon on 1942 he decided to head east to join the allies.
In the night between march 13th and 14th, the japanese squadron intercepted them near Nishitori Jima Island (actual Truong Sa islands) . The battle started with a heavy torpedo attack from the japaneses . Several hited the Voltaire, but the Danton class ships had yet demonstrated their survival capability against such type of attack. The riposte by the french ship severly damaged the Kako (renamed Abhakara Kiartivongse) which finally sunk of Itu Aba island. With their main ship lost the japaneses were forced to retreat.
The Voltaire was grounded on Namyit island to prevent it from sinking and evacuate the survivors he remained there and was scrapped after the end of hostilities. The Diderot returned to indochina after the war but was destroyed by an internal explosion while anchored in Haïphong, probably a Vietcong sabotage. The Thao Suranari survived war and was returned to Thailand navy and remained in service until he suffer heavy damages in 1951 during an attempted coup.
Ps: do my credits are correct?