| Official Name: | Sai Mun |
| Native Name: | ทรายมูล |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Yasothon |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Sai Mun |
| Subdivision Type3: | Tambon |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 31092 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 35170 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 3502 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 15.9394°N 104.2089°W |
Sai Mun (Thai: ทรายมูล, in Thai pronounced as /sāːj mūːn/) is a district of Yasothon province in northeastern Thailand.
Sai Mun village was formerly a village of Yasothon District, when it was still part of Ubon Ratchathani province. The village changed locations around the time of King Rama V when an epidemic caused villagers to abandon their homes and start a new village two kilometers away. At the site of their new village, which is present-day Sai Mun village, the villagers brought sand and soil from various sacred and revered places, and scattered it around the perimeter of their new home, to drive off the epidemic. It was from this ceremony that the village received its name.
Later, Sai Mun was given tambon status, and in 1968, Sanitary district (khet sukhaphiban) Sai Mun was created.[1]
After the separation of Yasothon from Ubon in 1972, on 15 May 1975, Sai Mun was elevated to a minor district (king amphoe), taking four tambons from Mueang Yasothon District: Sai Mun, Du Lat, Dong Mafai, and Na Wiang.[2]
In 1978, tambon Phai was reassigned from Kut Chum district to King Amphoe Sai Mun.[3]
On 26 July 1984, the minor district was elevated to a district,[4] and on 25 May 1999 Sanitary District Sai Mun was elevated to township (thesaban tambon) status.
Neighboring districts are (from the northeast clockwise) Kut Chum and Mueang Yasothon of Yasothon Province, and Selaphum of Roi Et province.
The district is divided into five sub-districts (tambons) with 53 villages (mubans).
| No. | Name | Thai name | Villages | Pop. | |
|---|---|---|---|---|---|
| 1. | Sai Mun | ทรายมูล | 16 | 4,890 | |
| 2. | Du Lat | ดู่ลาด | 12 | 4,426 | |
| 3. | Dong Mafai | ดงมะไฟ | 9 | 5,740 | |
| 4. | Na Wiang | นาเวียง | 7 | 3,958 | |
| 5. | Phai | ไผ่ | 9 | 5,900 |
As of 2003, Sai Mun had 25 primary schools with 2,737 students.
As of 2003, Sai Mun had two secondary schools with 1,724 students: