Nong Phrao Ngai (, ) is one of the seven subdistricts (tambon) of Sai Noi District, in Nonthaburi Province, Thailand. Neighbouring subdistricts are (from north clockwise) Thawi Watthana, Bang Khu Rat, Ban Mai, Khlong Yong and Naraphirom. In 2020 it had a total population of 7,595 people.
The subdistrict is subdivided into 12 administrative villages (muban).
The whole area of the subdistrict is covered by Nong Phrao Ngai Subdistrict Administrative Organization ().