Chian Yai (Thai: เชียรใหญ่, pronounced [t͡ɕʰīa̯n jàj]) is a district (amphoe) in the southeastern part of Nakhon Si Thammarat province, southern Thailand.

Neighboring districts are (from the north clockwise): Pak Phanang, Hua Sai, Cha-uat, and Chaloem Phra Kiat.

The minor district (king amphoe) on 1 February 1937 by splitting it from Pak Phanang district. It was upgraded to a full district on 3 November 1947.

The district is divided into 10 sub-districts (tambons), which are further subdivided into 98 villages (mubans). Chian Yai is a township (thesaban tambon) which covers parts of tambons Chian Yai, Tha Khanan, and Thong Lamchiak. There are a further nine tambon administrative organizations (TAO).

No. Name Thai name Villages Pop. 1. Chian Yai เชียรใหญ่ 10 4,210 3. Tha Khanan ท่าขนาน 11 2,989 4. Banklang บ้านกลาง 4 1,037 5. Ban Noen บ้านเนิน 10 3,144 6. Sai Mak ไสหมาก 11 4,900 7. Thong Lamchiak ท้องลำเจียก 10 4,816 10. Suea Hueng เสือหึง 11 3,030 11. Karaket การะเกด 12 7,371 12. Khao Phra Bat เขาพระบาท 9 6,849 13. Mae Chao Yu Hua แม่เจ้าอยู่หัว 10 7,481

Missing numbers belong to tambons which now form Chaloem Phra Kiat.

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