I examine Mòpyar Gaing: a new Buddhist sect that came to prominence in Myanmar in the 1980s and its founder monk; U Nyanar, who was arrested in the early 1980s for propagating the concept of ‘this-worldly karma’, which posed a major challenge to traditional beliefs in karmic causality and rebirth in the conservative Theravada tradition. The article examines how his re-interpretation of Buddhist doctrine brought against him charges of heresy and eventually led to lengthy prison terms until his release in 2016.