Wat Pa Sak is located outside the city walls, approximately one kilometer to the west of Chiang Saen in Tambon Wiang is Wat Pa Sak, which used to be the resedence of the patriarch. When King Saen Phu built the temple in 1295, three hundred teak trees were planted hence the name Pa Sak (Teak Forest). With ornamental stucco motifs, the temples chedi, which is 12.5 meters tall with a base of 8 meters wide, is regarded as being one of the most beautiful examples of Lanna architecture in northern Thailand.
Wat Pa Sak, ‘The Teak Forest Monastery’ owes its name to the teak trees which still stand along the perimeter of Chiang Saen’s city walls, which are located just a few hundred meters from this monastery. Its principle item of interest is a brick and stucco chedi dating from around 1319 (some chronicles indicate 1295, but that is unlikely since it is earlier than the founding of Chiang Saen). The chedi enshrines a relic from Pataliputra in India. Stylistically, it is influenced by Mon design which favored stacked square tiers with standing Buddhas embedded in each tier. It also shows Sukhothai influence in the detail of stucco work that survives on one of the higher tiers.
Apart from the chedi, the ruins of an ubosot with several standing stone columns can be found in front of the chedi. There are also scattered stone foundations of indeterminate purpose in the fields surrounding the site.