Area - 22.841 km2 (8.819 sq mi)
Population - 106,657
The name Lak Si means the fourth milestone. The community here was called Lak Si because of the fourth milestone of Khlong Prem Prachakhon (คลองเปรมประชากร) dug during King Chulalongkorn linking Bangkok toward Bang Pa-In. Lak Si became a district on 21 November 1997, separating from Don Mueang district.
- Government Complex Commemorating His Majesty The King's 80th Birthday Anniversary, 5 December, B.E. 2550 (2007)
- Wat Lak Si
- Chulabhorn Research Institute