Petitions addressed to some established authority are important historical sources for a study of colonial Cambodia, especially a colonial history from below. These documents, mostly fragments, inscribed, directly, or subtly, emotions and mentalities, actions and reactions, of ordinary people who usually were silenced in the historical records. The petitions were not uncommon practice in hierarchical society of pre-colonial era that carried over, in more effective form and practice and for everyone, at least in principle, into the colonial Cambodia. This paper examines the uses of petitioning as an act of protesting of ordinary people. Focusing in late nineteenth- to early twentieth-centuries Cambodia, this paper shows how ordinary people deployed petitioning process to protest against coercive and abusive actions of Khmer authorities, the agent of both traditional and colonial power, and also oppressive policies of the colonial administration. Therefore, it also means ordinary people exploited the petition to challenge the colonial power itself. Petition became a new terrain of passive resistance. However, little by little, petitioning process also shaped ordinary people to conform to colonial projects and practices.