| Official Name: | Si Somdet |
| Native Name: | ศรีสมเด็จ |
| Native Name Lang: | th |
| Settlement Type: | District |
| Subdivision Type: | Country |
| Subdivision Name: | Thailand |
| Subdivision Type1: | Province |
| Subdivision Name1: | Roi Et |
| Subdivision Type2: | Seat |
| Subdivision Name2: | Si Somdet |
| Subdivision Type3: | Subdistrict |
| Subdivision Type4: | Muban |
| Established Title: | District established |
| Population Total: | 37161 |
| Population As Of: | 2005 |
| Blank Name Sec1: | Postal code |
| Blank Info Sec1: | 45000 |
| Blank Name Sec2: | Geocode |
| Blank Info Sec2: | 4516 |
| Timezone: | ICT |
| Utc Offset: | +7 |
| Coordinates: | 15.9872°N 103.5108°W |
Si Somdet (Thai: ศรีสมเด็จ, in Thai pronounced as /sǐː sǒm.dèt/; ศรีสมเด็จ, in Lao pronounced as /sǐː sǒm.dět/) is a district (amphoe) in Roi Et province, Thailand.
Neighboring districts are (from the north clockwise): Mueang Roi Et and Chaturaphak Phiman of Roi Et Province; Wapi Pathum, Kae Dam, and Mueang Maha Sarakham of Maha Sarakham province.
The district was created on 1 April 1987, when the five tambons, Pho Thong, Si Somdet, Mueang Plueai, Nong Yai, and Suan Chik were split off from Mueang Roi Et district.[1] It was upgraded to a full district on 4 July 1994.[2]
The district is divided into eight sub-districts (tambons), which are further subdivided into 82 villages (mubans). There are no municipal (thesaban) areas; there are eight tambon administrative organizations (TAO).
| No. | Name | Thai name | Villages | Pop. | ||
|---|---|---|---|---|---|---|
| 1. | Pho Thong | โพธิ์ทอง | 7 | 2,877 | ||
| 2. | Si Somdet | ศรีสมเด็จ | 13 | 6,079 | ||
| 3. | Mueang Plueai | เมืองเปลือย | 8 | 3,075 | ||
| 4. | Nong Yai | หนองใหญ่ | 10 | 3,883 | ||
| 5. | Suan Chik | สวนจิก | 14 | 5,447 | ||
| 6. | Phosai | โพธิ์สัย | 10 | 8,043 | ||
| 7. | Nong Waeng Khuang | หนองแวงควง | 12 | 4,926 | ||
| 8. | Ban Bak | บ้านบาก | 8 | 2,831 |