The Sustainable Development Goal (SDG) 11 targets in Southeast Asia, particularly in Indonesia, Malaysia, and Vietnam, are closely aligned with urban spatial planning as a key tool for achieving sustainable cities. Big Earth Data offers transformative potential in tackling sustainable development challenges in the region by enabling advanced analytics on large datasets, such as satellite imagery and geospatial information. To harness this potential, we propose the development of a Science-Based Urban Spatial Planning (SciBUSP) initiative, which utilises satellites, geospatial data, and artificial intelligence (AI)-driven analytics to monitor vulnerable regions, optimise resource allocation, mitigate urban sprawl, and enhance resilience. A goal of this initiative is capacity-building designed to empower young scientists and early-career professionals across Southeast Asia. Through mentor-based training, national training, and networking, participants will be equipped to apply big earth data within the SciBUSP framework. The methodology encompasses preparatory coordination, methodological development, system prototyping, capacity building, evaluation, and dissemination. The SciBUSP toolkit will be piloted in chosen cities to ensure contextual relevance. Trained young scientists will then transfer knowledge to their respective stakeholders in their home countries, supporting local expertise and advancing evidence-based planning aligned with SDG 11.