Activists, non-governmental organizations (NGOs) and the international media have repeatedly singled out the Mekong region as a hotspot for ‘sex trafficking’. Yet, in recent years anti-trafficking campaigns that focus on prostitution have lost momentum, witnessed by a decline in project activity and media attention. This article suggests that a moral panic relating to prostitution has partly been overshadowed by a broader focus on the Thai labour sector, particularly the fishing industry. At the same time, this shift coincides with a discursive reorientation away from ‘trafficking’ towards ‘modern slavery’. This article explores the gendered dimensions of this shifting regime of migration governance which in effect replaces women and girls with men and boys as the central locus for action. Although this change must be understood in light of structural changes within the Thai economy and a broader compassion and programme fatigue, this article points to the similar moral registers that both ‘sex trafficking’ and ‘slavery at sea’ invoke. Neoliberal modes of activism coupled with emergent social media help explain why anti-trafficking and modern slavery discourses have gradually redirected attention away from sex to fish.