Sirikit Dam or formerly known as “Pha Som Dam” is the largest earth-fill dam in Thailand. It was built across the Nan River at Khao Pha Som, Pha Leud Sub-district, Tha Pla District, Uttaradit Province under the Nan River Basin Development Project of the Royal Irrigation Department. The construction started in 1968 and completed in 1972. Sirikit Dam helps to relieve flooding in Nan River basin and together with Bhumibol Dam relieves flooding in Chao Phraya Central Plains. With Sirikit Dam, there are irrigation areas in Nan River basin in the rainy season of 1,551,000 rai and in the dry season of 300,000 rai, and in the Chao Phraya Central Plains of 2,500,000 rai totaling 2,800,000 rai. When dredging and dressing some parts of the Nan River, it can be used for a transport route from Nakhon Sawan to Uttaradit all year round. The reservoir of Sirikit Dam serves as a fish breeding and a tourist spot. With the royal permission of His Majesty King Bhumibol Adulyadej The Great, the name of the dam was changed to Sirikit Dam after Her Majesty Queen Sirikit The Queen Mother.

On March 4, 1977, the opening ceremony of the dam was performed by Their Majesties King Bhumibol Adulyadej The Great and Queen Sirikit The Queen Mother accompanied by Her Royal Highness Princess Maha Chakri Sirindhorn.