Filtration tests on soil-geotextile filter systems were conducted in the laboratory in order to evaluate the filtration and clogging performance of prefabricated vertical drain (PVD) geotextile filter jackets in soft Bangkok clay. Initially, the flow was very slow for all types of PVD geotextile filter jackets and the soil permeability characteristics controlled the flow behavior. Subsequently, flow increased with time followed by a loss of fine particles. Finally, flow decreased and reached an equilibrium stage. As a result of the laboratory filtration tests, filtration and clogging criteria are proposed for geotextile filter jackets on PVDs in soft Bangkok clay.