So Phisai (Thai: โซ่พิสัย, pronounced [sôː pʰí.sǎj]) is a district (amphoe) of Bueng Kan province, northeastern Thailand.

The minor district (king amphoe) So Phisai was established on 1 March 1972, when the three tambons So, Si Chomphu, and Nong Phan Tha were split off from Phon Phisai district.

[2] Neighboring districts are (from the west clockwise): Fao Rai and Rattanawapi of Nong Khai province; Pak Khat, Mueang Bueng Kan, and Phon Charoen of Bueng Kan Province; and Ban Muang of Sakon Nakhon province.

The district is divided into seven sub-districts (tambons), which are further subdivided into 89 villages (mubans).

This Bueng Kan province location article is a stub.