This thesis discusses the importance and use of flexibility in urban planning and design in South East Asian new urban developments. It stretches the importance of a new balance between the stakeholders in order to create more resilient and sustainable urban extensions. In this way it tries to find answers to the question; in what way can flexibility, understood as the ability for modification and adaptation in plan and process, be incorporated in the contemporary urban planning model and the urban design of new urban areas in Hanoi? The site, Nam An Khanh, in Hanoi serves as a test case for a new, more flexible, framework for development in New Urban Areas in Hanoi. The research explores the applicability of various design and planning tools that foster adaptability and sustainability, that are based on research and experience in the western world.