A Common Pool Resource (CPR) is a natural or man-made resource system with open or widespread access where the resources are depletable with increased use. CPR examples include forests, pastures, irrigations, rivers, lakes, and fisheries. This research examines a common pool resource in Thailand, i.e. a canal in Nonthaburi Province (NP). The canal, named Klong Om-Klong Bangkok Noi-Klong Bang Kruai, is utilised for agriculture, transportation, commerce, tourism and aesthetics. Currently, urbanisation threatens the canal through changes in land use along the canal. Also, an increasing amount of garbage and water hyacinths in the canal are degrading the quality of the canal environment and waterway transportation. The aims of this thesis were to identify essential factors in the canal system that support the success of collective action in environmental management. This study analyses CPR management in the NP canal system by applying design principles illustrated by long-enduring CPR institutions. These have been identified by Elinor Ostrom (Ostrom, 1990; 1992) and by analysing the situational variables as barriers or resources for collective action. The research was conducted on five communities in Thailand. The primary data collection techniques were qualitative and consisted of two different interview processes and five focus groups. The interviews were completed with local residents and government officials while the focus groups were completed with individuals from five communities. The N6 computer program for handling qualitative data was used to analyse the responses.