The examination of gill parasites from Pangasius krempfi Roberts & Vidthayanon, 1991 ; P. kunyit Pouyaud et al., 1999 ; P. mekongensis Gustiano et al., in press and P. sabahensis Gustiano et al., in press (Siluriformes, Pangasiidae) in Southeast Asia revealed the presence of six species of Monogenea, all belonging to the genus Thaparocleidus Jain, 1952 (Monogenea, Ancylodiscoididae) as defined by Lim (1996) and Lim et al. (2001). One has been previously described (T. vietnamensis Pariselle et al., 2002), five are considered as new species : T. humerus n. sp. and T. culter n. sp. on P. kunyit ; T. mehurus n. sp. and J. culteroides n. sp. on P. sabahensis ; and T. phuongi n. sp. on the four studied host species. The latter one, due to slight morphometric differences linked to geographical origin of hosts, is described as made up of three sub-species : T. phuongi phuongi n. sub-sp., T. phuongi malaysiensis n. sub-sp. and T. phuongi indonesiensis n. sub-sp.