Attempts to view it are redirected to a splash screen from the Ministry of Information and Communications Technology, which reads "this website has inappropriate content and has been suspended."
In recent weeks HRW have heavily criticised Thailand's military government for its crackdown on dissent.
"The fact that the (junta) feels the need to block Human Rights Watch's Thailand webpage means that we must be doing something right," said Brad Adams, HRW's Asia director.