Lam Dom Noi (Thai: ลำโดมน้อย, in Thai pronounced as /lām dōːm nɔ́ːj/; ลำโดมน้อย, in Lao pronounced as /la᷇m dōːm nɔ̂ːj/) is a tributary of the Mun River. It originates in the Dângrêk Mountains and flows northwards. The watercourse passes Buntharik district and is stopped by the Sirindhorn Dam in Chong Mek Subdistrict, Sirindhorn district. It is 150km (90miles) long.
The Sirindhorn reservoir is the biggest water resource of Ubon Ratchathani province.