The dwarf loach, ladderback loach, pygmy loach, chain loach or chain botia, (Ambastaia sidthimunki) is a freshwater fish belonging to the family Botiidae. Formerly included in the genus Yasuhikotakia, it is frequently seen in the aquarium trade, the product of captive breeding. This endangered species is endemic to the Mae Klong basin (including Khwae Noi River) in Thailand, and the Ataran River on the Thai-Myanmar border. Records from the Mekong basin are misidentifications of the very similar and closely related A. nigrolineata.