Phra Chulachomklao Fort is included because it is arguably one of the best preserved coastal batteries still mounting the original 6-inch Hydropneumatic (H.P.) Disappearing Guns manufactured by Sir W.C. Armstrong, Mitchell & Co.
This seven-gun battery was built by King Rama V (King Chulalongkorn, 1868-1910) who wished to provide protection form attack by foreign naval forces up the Chao Phraya River that gives access to Bangkok. Phi Suea Samut Fort on the Island of Pak Khlong Bang Pla Kot was located about 9 miles further upriver as a supporting fort.
The coastal defence battery was built over an existing fort, the footing of which remain in some parts. It covers the estuary of the Chao Phraya River. Construction started in 1884 and the battery was not completed until 1893. It was armed with seven disappearing guns, and had an engine room, magazine and shelters built into the complex.
On the 13th July 1893, the newly completed battery, under the command of a Dutch mercenary soldier, engaged two French warships. These were the “Inconstant”, built in 1886 and armed with a single 3.9-inch gun, and five Hotchkiss one pounders (similar to a Gatling), and “Comete” with one 139mm gun, two 90mm guns and two to four 37mm guns. Both these vessels were steam ship, but started under tow from the sail ship, Jean Baptiste Say. It has been suggested that this was possibly to protect the two gunboats from any minefield covering the estuary. The Jean Baptiste Say was damaged by fire and later captured but the two gunboats broke through the defences and reached Bangkok. For more details see here.
The Battery remains intact with all the original guns. Renovated in 2018 and now open to the public.
Details of the linked Fort Phi Sua Samut can be found here.
For more background information on Disappearing guns in British use, follow this link.