A study of the hitherto unreported Stichoneuron halabalensis Inthachub led to the characterization of the known compounds (+)-α-tocopherol and (R)-(+)-goniothalamin; four known Stemona alkaloids, bisdehydoxystemoninine A (1), stemoninine (2), sessilistemonamine C (3 ) and sessilistemonamine A (4); and three new alkaloids, stichoneurine C (5), D (6) and E (7). The structures of these compounds were determined on the basis of their spectroscopic data. Alkaloid 7 showed significant inhibitory activity against electric eel acetylcholinesterase (AChE) (IC50 5.90±0.084 μM), while goniothalamin and compounds 1 and 2 showed significant inhibitory activities against human AChE (IC50 7.24±0.52, 5.52±0.13 and 3.74±0.09 μM, respectively).