Nikhom Kham Soi (Thai: นิคมคำสร้อย, pronounced [ní(ʔ).kʰōm kʰām sɔ̂j]; Northeastern Thai: นิคมคำสร้อย, pronounced [nì(ʔ).kʰo᷇m kʰa᷇m sɔ̀j]) is a district (amphoe) of Mukdahan province, northeastern Thailand.

Neighboring districts are (from the west clockwise) Nong Sung, Mueang Mukdahan and Don Tan of Mukdahan Province, and Loeng Nok Tha of Yasothon province.

The minor district (king amphoe) was established on 2 June 1975, when the five tambons Nikhom Kham Soi, Na Kok, Na Udom, Nong Waeng, and Kok Daeng were split off from Mukdahan district.

The district is divided into seven sub-districts (tambons), which are further subdivided into 79 villages (mubans).

Nikhom Kham Soi is a township (thesaban tambon) which covers parts of the tambon Nikhom Kham Soi, Na Kok, and Chok Chai.