The SEA-PLM 2024 survey was designed to provide robust, representative, and comparable data on learning outcomes among Grade 5 students across participating Southeast Asian countries. The population coverage and sampling methodology ensured that the survey accurately reflected the diversity of students and schools within each education system while meeting international standards for large-scale assessments. This report describes the target population, sampling design, school and student selection procedures, coverage requirements, and quality assurance measures implemented to ensure the reliability and comparability of SEA-PLM 2024 results across countries.