Bang Sao Thong (Thai: บางเสาธง; pronounced [bāːŋ sǎw tʰōŋ]) is a district (amphoe) of Samut Prakan province in central Thailand.

Neighboring districts are Lat Krabang to the north, Bang Bo to the east and Bang Phli to the west.

Bang Phli New Town (Thai Mueang Mai Bang Phli) was established between 1992 and 1993 as a residential area for high-income families. The area around the new town, comprising three tambons, was then split off from Bang Phli district and formed the new minor district (king amphoe), becoming effective on 1 April 1995.

The Thai government, on 15 May 2007, upgraded all 81 minor districts to full districts. On 24 August 2007 the upgrade became official.

Nissan has an automobile factory in the district. Nissan produces hybrid electric vehicles (HEVs) there based on its e-Power technology as well as batteries for electric vehicles. It has a production capacity of 370,000 vehicles a year.

The district is divided into three sub-districts (tambon), which are further subdivided into 39 villages (muban). Bang Sao Thong is a township (thesaban tambon) which covers parts of tambon Bang Sao Thong and Sisa Chorakhe Yai. Each of the tambons has a tambon administrative organization (TAO) responsible for non-municipal areas.

No.	Name	Thai name	Villages	Pop.
1.	Bang Sao Thong	บางเสาธง	17	52,488
2.	Sisa Chorakhe Noi	ศีรษะจรเข้น้อย	10	12,986
3.	Sisa Chorakhe Yai	ศีรษะจรเข้ใหญ่	12	12,045

• amphoe.com