At first the area was administered from Bang Bua Thong District. On 1 January 1948 four sub-districts were split off to form the new minor district (king amphoe) Sai Noi.[1] On 6 June 1956 it was elevated to full district status.[2]
In 1959 Tambon Khun Si was transferred from Bang Len District (Nakhon Pathom) to become part of Sai Noi.[3]
In 1979 the southern part of Tambon Rat Niyom formed the new tambon, Khlong Khwang.[4] The following year the southern part of Tambon Sai Noi was split off to create Tambon Thawi Watthana.[5]
Economy
One of the world's leading tropical seed companies, East-West Seed (EWS), has its global headquarters in the district.[6][7] EWS was named the world's top-ranked number seed provider to smallholder farmers by the Amsterdam-based Access to Seeds Foundation.[8]
Most areas of Sai Noi are still rural. Most residents have a rice farming career.
Administration
The district is divided into seven sub-districts (tambons), which are further subdivided into 68 villages (mubans). Sai Noi itself has sub-district municipality status (thesaban tambon) which covers parts of tambons Sai Noi and Khlong Khwang. There are a further seven tambon administrative organizations (TAO).