Sarit Phong Dam (Thamnop Phra Ruang)

An earthen embankment strung between two low hills about 2 km southwest of Sukhothai’s old city wall, Sarit Phong Dam — also called Thamnop Phra Ruang — is one of the few Sukhothai-era structures named in the Ramkhamhaeng Inscription, Thailand’s oldest surviving stone text. It’s free to visit, technically inside the boundary of Sukhothai Historical Park but well outside the paid old-city zone, and gets a fraction of the visitors that the main temple ruins do.

The dyke runs in the gap between Khao Phra Bat Yai and Khao Kiu Ai, holding back monsoon runoff in what would otherwise have been a natural drainage channel toward the city. Estimates put its historical storage capacity at around 400,000 cubic metres, with water led out through canals — including the old Khlong Sao Hai — toward Sukhothai’s moat and reservoir system. Whether it functioned mainly as a reservoir for irrigation and city water supply, or primarily as flood control steering rain away from the walls, is still debated among historians; the inscription confirms the structure’s age and importance without settling the argument. Either reading makes it one of the earliest known examples of organised water management in Thailand, built centuries before the country had anything resembling a modern dam.

Little of that history is signposted on-site. What you actually find is a broad grassy embankment you can walk along, water on one side and rice paddies and fish ponds on the other, with a scatter of local farmhouses nearby. Fishermen work the water in small wooden boats, and it’s common to see water buffalo wading through the shallows in the early morning. Insider Tip: Go at sunrise or in the last hour before sunset — the water turns still and reflective, and the heat that makes midday visits uncomfortable hasn’t built up yet.

Watch out: Signage is minimal and English information is close to nonexistent. There’s no public transport out here — you’ll need a motorbike or car from Sukhothai town, and asking a local for the turn-off is often more reliable than trusting a map app’s last few hundred metres.

Pair it with a quiet loop through Sukhothai’s outer historical zone rather than treating it as a standalone trip — most visitors give it 30-45 minutes, enough to walk the embankment and take in the rural setting before heading back toward the main temple complex.