Pom Thung Setthi Fort

The fort is laterite on a square plan with arrowhead bastions at the four corners, like a European star fort. Its walls are about 6 m high and 3.5 m thick at the base; it measures about 82 m from bastion tip to bastion tip, with curtain walls of about 52 m, each pierced by a central gate. The 83.5 m-per-side figure quoted in some places has not been confirmed.

Along the top runs a row of sema-shaped merlons, each with a horizontal gun-loop below. The inner walls have pentagonal, gable-like niches, some with windows to the outside. The interior is an open yard with no buildings. The north wall has been demolished, so three sides stand; a walkway runs along the wall top and there are rooms in its base. The name Thung Setthi seems to come from the local name of the field, also used for amulets from nearby crypts; no source says who named it.

Scholars date it to the Ayutthaya period, roughly the 16th–17th centuries. Some sources link its design to the Portuguese, who began supplying guns and mercenaries to Siam under King Ramathibodi II from 1518, but this remains a hypothesis without direct records.

Together with the Ping, the fort formed a first line of defence against attacks from the west, such as from Hanthawaddy and the Mon, and controlled river traffic past Kamphaeng Phet and Nakhon Chum.

It was registered as an ancient monument in the Royal Gazette on 26 June 1962, covering 10 rai 2 ngan that reach beyond the walls into old Nakhon Chum, according to lovethailand.org. No date for Fine Arts Department restoration was found.

The fort is open-air and can be visited any day in daylight, free, with no ticket booth; allow 20–40 minutes. From town, cross the Ping bridge to Nakhon Chum, about 10 minutes; no regular public transport reaches the gate. There is little shade and no toilets, so come in the morning or evening, and do not climb the walls or chip the laterite.