The original Phi Sua Samut Fort. Thailand was built in 1819 and it was shaped like a butterfly. Initially armed with smooth bore guns, it is still possible to see some of the old gun embrasures on the West and East arms of the fort.
The new battery with three disappearing 6-inch gun was built about 1893m the same time as the seven gun battery at Phr Culachomklao Fort, see … In July 1893 just a few months after the fort was completed they failed to stop two French gunboats sailing up the river to the centre of Bangkok. It is likely that the artillerymen were at this time barely trained to operate the guns.
Until 2006 the Fort was in the hand of the Navy and can now be accessed on foot. A well preserved and excellent example of a disappearing gun battery.
Details of the linked Fort Chukachomklao can be found at https://pinkroutes.com/poi/phra-chulachomklao-fort/.
For more background information on Disappearing guns in British use, follow this link.