Not to be confused with the small Wat Umong in the old city, this historic forest wát is famed for its sylvan setting and its ancient chedi, above a brick platform wormholed with passageways, built around 1380 for the 'mad' monk Therachan. Keep an eye out for the Sri Lankan–style stupa, and as you wander the arched tunnels, look for traces of the original murals and several venerated Buddha images.
The scrub forest around the platform is scattered with centuries' worth of broken Buddha images. The attendant monks raise cows, deer, chickens and, curiously, English bull terriers, and in the grounds is a pretty artificial lake, surrounded by gù·đì (monks' quarters). Check out the emaciated black-stone Buddha in the Burmese style, behind the chedi.