Abstract
This study investigated the evolving trajectories and influencing factors of Thai majors' language learning motivation in Chinese universities. Drawing on retrospective motivational mapping and semi-structured interviews with 21 participants, the study employed grounded theory to analyze motivational changes across 4 years of undergraduate study. The findings revealed that students' motivation was characterized by sharp fluctuations, early-stage rises from low baselines, a significant decline during the sophomore-to-junior transition, and erratic shifts in the final year. Despite some common trends, individual motivational paths displayed considerable diversity. Grounded theory analysis further identified four interconnected systems-macro, exo, proximal, and habitual-that collectively shaped learners' motivational dynamics. Notably, many Thai majors entered their programs with relatively low initial motivation, contrasting with findings from studies on major world languages. In addition, learners' motivation was highly sensitive to macro-level influences such as political events, and overseas exchange experiences did not yield the motivational gains commonly reported in Western study-abroad contexts. The study makes two key contributions: theoretically, it extends the explanatory scope of motivation research to less commonly taught languages by constructing a visualized, multi-layered model within the framework of complex dynamic systems theory; practically, it provides insights for curriculum design, student support, and policy development by highlighting critical phases and contextual influences on motivational sustainability.