Thung Yai (Thai: ทุ่งใหญ่, pronounced [tʰûŋ jàj]) is the westernmost district (amphoe) of Nakhon Si Thammarat province, southern Thailand.

Tambon Ku Rae was separated from Thung Song district and made the minor district (king amphoe) Ku Rae in 1906.

[1] Neighboring districts are (from the north clockwise): Tham Phannara, Chawang, Na Bon, Thung Song, Bang Khan of Nakhon Si Thammarat; Lam Thap, Khao Phanom of Krabi province; and Phrasaeng of Surat Thani province.

The district is divided into seven sub-districts (tambons), which are further subdivided into 63 villages (mubans).

This Nakhon Si Thammarat Province location article is a stub.