Thung Sai (Thai: ทุ่งทราย, pronounced [tʰûŋ sāːj]) is a tambon (subdistrict) of Sai Thong Watthana District, in Kamphaeng Phet Province, Thailand.

[1] The subdistrict was created effective September 15, 1972 by splitting off 7 administrative villages from Wang Yang.

[2] The tambon is subdivided into 17 administrative villages (muban).

The whole area of the subdistrict is covered by the subdistrict municipality (Thesaban Tambon) Thung Sai (เทศบาลตำบลทุ่งทราย).

This Kamphaeng Phet Province location article is a stub.