Wat Phra Singh is an important Buddhist temple within the old city walls. King Ananda Mahidol (Rama VIII), the older brother of the late King Bhumibol Adulyadej (Rama IX), bestowed on it the status of Royal temple of the first grade in 1935. Construction on Wat Phra Singh began in 1345 when King Phayu, the fifth king of the Mangrai dynasty, had a chedi built to house the ashes of his father King Kham Fu. A wihan and several other buildings were added a few years later and the resulting complex was named Wat Lichiang Phra. When, in 1367, the statue of Phra Buddha Singh was brought to the temple, the temple complex received its present name. During restoration works in 1925, three funerary urns were discovered inside a small chedi. It was assumed that these contained royal ashes. The urns have since been lost. From 1578 to 1774 the Burmese ruled Lanna and in this period the temple was abandoned and came under serious disrepair. It was only when King Kawila assumed the throne as King of Chiang Mai in 1782, that the temple was restored. King Kawila had the ubosot built and the chedi enlarged. Later successors restored the Wihan Lai Kham and the elegant Ho Trai (temple library).
The whole temple complex underwent extensive renovations under the famous monk Khru Ba Srivichai during the 1920s. Many of the buildings were again restored in 2002.
The important features of Wat Phra Singh are:-
Wihan Luang - the original wihan was replaced by the present building in 1925
Wihan Lai Kham - built in 1345 to house the Phra Buddha Singh statue, a prime example of classical Lanna architecture
Ubosot – built in 1806 containing a copy of the Emerald Buddha
Ho Trai – the temple library
The Phrathatluang – built in 1345, the chedi was enlarged several times
The Kulai chedi - built as a pagoda with five tiered roofs by King Mueangkaeo (1495–1525) and restored (1813–1822)

Source: Wikipedia