Amblyceps protentum is described herein as a new species of amblycipitid catfish from the Salween River drainage in western Thailand. It can be distinguished from Indochinese congeners except for A. kurzii by a more elongate, slender body most evident in the smaller body depth at anus (8.0–11.0% SL vs. 10.7–16.9) and caudal peduncle depth (8.0–10.3% SL vs. 10.1–15.9). It differs from A. kurzii in having a longer adipose-fin base (18.8–22.7% SL vs. 15.1–18.3) and larger eye (diameter 6.9–8.8% HL vs. 5.1–5.8). Amblyceps protentum is further diagnosed by the following combination of characters: predorsal length 24.1–28.9% SL, length of dorsal-fin base 10.5–13.2% SL, dorsal-to-adipose distance 26.3–32.2% SL; head width 12.1–15.0% SL, total vertebrae 41–42, an incomplete lateral line and deeply forked caudal fin with poorly-developed projections on proximal lepidotrichia of median rays. The taxonomic status of A. caecutiens and A. kurzii are discussed and a neotype designated for A. caecutiens. This neotype designation makes A. mucronatum a junior subjective synonym of A. caecutiens.