Academic achievement in Thai educational contexts faces ongoing challenges despite extensive research efforts. This systematic review addresses critical gaps in understanding factors affecting academic achievement by synthesizing findings from multiple Thai studies to provide evidence-based insights for educational practice. Following PRISMA methodology, this systematic review analyzed 214 research studies from an initial pool of 10,249 articles identified through Google Scholar using Publish or Perish software. Studies conducted between 1987-2024 examining factors influencing academic achievement in Thai educational contexts were systematically reviewed using inclusion criteria requiring correlational research with available correlation coefficients. Five core factors emerged as most influential in academic achievement: Learning Attitude (43.93% frequency), Achievement Motivation (40.65%), Teaching Quality (35.51%), Prior Knowledge (31.78%), and Classroom Climate (28.97%). These factors demonstrate both direct and indirect relationships with academic outcomes, operating through complex networks of influence that combine individual characteristics with environmental conditions. Academic achievement in Thai contexts is predominantly influenced by affective factors (attitude and motivation) supported by cognitive foundations (prior knowledge) and environmental facilitators (teaching quality and classroom climate). The findings provide evidence-based guidance for educational interventions while highlighting the importance of cultural adaptation in applying universal educational theories to Thai educational settings.