This research investigates English acknowledgements in dissertations written by Thai PhD students, particularly the generic structure and linguistic patterns of gratitude expressions used in the acknowledgements. Following the line of the move analysis in acknowledgements of Hyland (2004), this article analyzed 70 acknowledgements accompanying PhD dissertations in the area of English language study. The study result shows that the generic structure comprises 3 moves: thanking, announcing, and signing-off. The first move is obligatory whereas the other two are optional. Various gratitude expressions are used in response to different assistance forms. Also, the study result reveals the aspects of politeness, social distance, and the family institution of the Thai culture.