The introduction of Child Presence Detection (CPD) technology under the Child Occupant Protection (COP) pillar in the New Car Assessment Programme for Southeast Asian Countries (ASEAN NCAP) Roadmap 2021-2025 should come with proper assessment methodology to evaluate the effectiveness of such technologies in a vehicle. This paper gives an overview of CPD systems and Vehicle Reminder Systems (VRS), together with their associated technologies. Most importantly, a comprehensive assessment methodology for CPD and VRS that covers the vehicle preparation, occupants’ classifications (i.e., newborn, infant and toddler), assessment procedure, scoring criteria, and implementation plan is also presented. It is hoped that this work could contribute to ASEAN NCAP Roadmap 2021-2025, and gives valuable insights to relevant stakeholders such as the vehicle manufacturers and technology providers.