The biggest reservoir in Central Thailand, the Pa Sak Cholasit Dam was constructed as part of the Maenam Pa Sak Royal Development Project, an initiative of King Bhumibol. Constructed in 1989, the earth (soil)-filled dam with a clay core was granted the name by His Majesty the King who presided over its opening on 25 November 1999. The Dam stretches over Lop Buri and Saraburi Provinces. It is 4,860 meters long with a capacity of 785 million cubic meters.

Pa Sak Cholasit Dam is a major source of water for household, agriculture and industrial use in Lop Buri and Saraburi Provinces. Moreover, it helps prevent flooding on the Pasak riverside and Bangkok and its outskirts. The dam also provides large-scale, fresh-water fish for locals.

An emerging tourist attraction, Pa Sak Cholasit Dam offers a unique opportunity to travel across the reservoir by train. The railway was constructed along the dams ridge which leads to Pa Sak Basin Museum and a scenic lookout point above the dam. The journey offers a breathtaking and refreshing view of the reservoir, and also a bed of sunflowers. It serves daily from 7.30 a.m.-18.00 p.m. The fare is 25 baht for adult and 10 baht for children.

Getting to Pa Sak Cholasit Dam is easy. By car from Lop Buri city, take Highway No. 3017 (Phatthana Nikhom Wat Mueang) for a total distance of 60 kilometers. It is highly recommended to take the trip by train during November January. The State Railway of Thailand operates a special route to and from Bangkok-Pa Sak Cholasit Dam every Saturday, Sunday and public holidays. For more information, contact tel: 02 223 7101 or 02 223 7020.