Sai Thong Watthana (, ) is a district (amphoe) of Kamphaeng Phet province, central Thailand.
Neighbouring districts are (from the south clockwise): Bueng Samakkhi, Khlong Khlung, and Sai Ngam of Kamphaeng Phet Province; and Sam Ngam of Phichit province.
The minor district (king amphoe) was established on 1 April 1992 by splitting off three tambons from Khlong Khlung district. Originally named Thung Sai after the central tambon, it was renamed Sai Thong Watthana in 1995. It was upgraded to a full district on 11 October 1997.
The district Sai Thong Watthana is subdivided into 3 subdistricts (Tambon), which are further subdivided into 38 administrative villages (Muban).
There is one subdistrict municipality (Thesaban Tambon) in the district:
There are 2 subdistrict administrative organizations (SAO) in the district: