Krasae Sin (Thai: กระแสสินธุ์, pronounced [krā.sɛ̌ː sǐn]) is a district (amphoe) in the northern part of Songkhla province, southern Thailand.

Neighboring districts are (from the south clockwise): Sathing Phra of Songkhla Province; Pak Phayun, Bang Kaeo, Khao Chaison, and Mueang Phatthalung of Phatthalung province; and Ranot of Songkhla Province.

The minor district (king amphoe) was created on 16 February 1978, when the three tambons, Choeng Sae, Ko Yai, and Rong, were split off from Ranot district.

[2] The district is divided into four sub-districts (tambons), which are further subdivided into 22 villages (mubans).

There are no municipal (thesaban) areas within the district; there are a further four tambon administrative organizations (TAO).