The temple, colloquially known as Wat In, was restored during the reign of King Rama I by Chao Inthawong, a member of the Lao royal family who settled in the area. Central Thailand's most famous monk, Somdet Phra Buddhachan (Somdet Toh) began construction of the giant standing Maitreya (Buddha-to-come) image in 1867 and it wasn't finished until 1927. The flame-like structure on top of the image's head contains relics of the Buddha which were donated by the Sri Lankan government in 1978. For Bangkok's Rattanakosin bicentennial celebration in 1982, the then Abbot, Phra Khru Woraphattikhun carried out restoration including decoration of the statue with 24-karat golden mosaic tiles from Italy. Entrance to the temple is free.
The impressive standing statue of Maitreya, known as Luang Phor Toh, is 32 meters tall by 11 meters wide and is one of the largest in Thailand. The bai sema boundary markers around the ordination hall (ubosot) are unusual in that they are supported by small nagas. Inside the ubosot are wall murals depicting scenes of daily life in ancient Siam. The area behind the ubosot has statues of Hindu deities and of Chao Mae Kuan Im, the Goddess of Mercy. There is also a shrine to Somdet Toh.