This study diverges from conventional psychological perspectives that often concentrate on language learning deficiencies necessitating remedial interventions. Instead, it emphasizes the pivotal role of positive psychological constructs in facilitating optimal language development, particularly in contexts characterized by limited exposure to English. Through an exploration of positive psychology dimensions among Thai EFL secondary school students, the research examined the nuanced interplay of positive psychological factors shaping language learning in such contexts. Employing an Exploratory Factor Analysis (EFA) with the inventory and interviews, this study examined the underlying psychological determinants guiding the language learning experiences of 255 Thai EFL secondary school students from diverse regions. Factor analysis, complemented by Kaiser-Meyer-Olkin (KMO) statistics, contributes to refining the inventory and reveals four crucial positive psychology factors that collectively explain 61.158% of the variance in positive psychology levels. The resultant 18-item, 4factor model encompasses processes within four categories of positive psychology constructs--"Engagement and Enjoyment," "Grit and Perseverance," "Interest and Focus," and "Future Intentions." This model culminates in the development of the EFL Positive Psychology Inventory (EFLPP), which exhibits commendable validity and reliability. Additionally, insights gleaned from semi-structured interviews elucidate three sources of L2 positive psychology constructs: "learning environment," "predetermined goals," and "personal interests." This study emphasizes the significance of these positive psychology constructs in informing pedagogical strategies aimed at cultivating efficacious language learning experiences. By elucidating learners' positive psychology constructs, the research attempts to equip English educators in EFL contexts with tailored instructional methodologies that align with learners' positive aspirations, thereby augmenting English language learning outcomes.