| Official Name: | Nong Ya Sai |
| Native Name: | หนองหญ้าไซ |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Suphan Buri |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Nong Ya Sai |
| Subdivision Type3: | Tambon |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 49272 |
| Population As Of: | 2013 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 72240 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 7210 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 14.775°N 99.9111°W |
Nong Ya Sai (th|หนองหญ้าไซ, pronounced as /th/) is a district (amphoe) in the western part of Suphan Buri province, central Thailand.
The minor district (king amphoe) was created on 1 June 1983, when the four tambons Nong Ya Sai, Nong Rathawat, Nong Pho, and Chaeng Ngam were split off from Sam Chuk district.[1] It was upgraded to a full district on 21 May 1990.[2]
Neighboring districts are (from the north clockwise) Dan Chang, Doem Bang Nang Buat, Sam Chuk, and Don Chedi of Suphan Buri Province, and Lao Khwan of Kanchanaburi province
Nong Ya Sai is divided into six sub-districts (tambons), which are further subdivided into 66 administrative villages (mubans).
| No. | Name | Thai | Villages | Pop.[3] | |
|---|---|---|---|---|---|
| 1. | Nong Ya Sai | Thai: หนองหญ้าไซ | 13 | 11,985 | |
| 2. | Nong Ratchawat | Thai: หนองราชวัตร | 8 | 5,120 | |
| 3. | Nong Pho | Thai: หนองโพธิ์ | 14 | 6,748 | |
| 4. | Chaeng Ngam | Thai: แจงงาม | 8 | 6,473 | |
| 5. | Nong Kham | Thai: หนองขาม | 11 | 8,981 | |
| 6. | Thap Luang | Thai: ทัพหลวง | 12 | 9,965 |
There is one sub-district municipality (thesaban tambon) in the district:
There are six sub-district administrative organizations (SAO) in the district: