Thawi Watthana (, ) is one of the seven subdistricts (tambon) of Sai Noi District, in Nonthaburi Province, Thailand. The subdistrict is bounded by (clockwise from north) Khun Si, Sai Noi, Phimon Rat, Bang Khu Rat, Nong Phrao Ngai and Naraphirom subdistricts. In 2020 it had a total population of 8,862 people.
The subdistrict is subdivided into 8 administrative villages (muban).
The whole area of the subdistrict is covered by Thawi Watthana Subdistrict Administrative Organization ().