In the very first year of his architectural studies at the Sir J.J. College of Architecture in Mumbai, Das got associated with the self-help redevelopment project of ‘Jaffar Baba’ slums in Bandra, Mumbai which was planned and designed by Planner D.G. Parab (then with CIDCO) and led by ‘BUILD’ – an NGO. It involved the reconstruction of about 200 houses and a community center including restructuring the overall layout. 
P K Das is a an architect and activist known for a dispensation towards "proper planning" and engagement with various players including state and developers, in his work on housing and open spaces for the urban population.
He is part of the Nivara Hakk Sangharsh Samiti movement for rehousing displaced urban poor, which has been active in fighting for and building on sites in Chandivali and Goregaon. Das has engaged with multiple groups and agencies for the creation of vision documents and actual developments of a public projects, including the seaside promenade in Bandra West, the "cleanup" of Juhu beach, post-earthquake shelters in Kutch, among others. Recently (2017) his office has done a detailed slum mapping of Mumbai (file?) based on which they have made a recommendation for integrated development of slums, unlike the small pockets which the SRA method creates.