This chapter provides the theoretical grounding for the study, drawing on key frameworks that illuminate how minority pupils experience language learning in multilingual contexts. Vygotsky’s socio-cultural theory forms the starting point, emphasizing the role of interaction, scaffolding, and the Zone of Proximal Development (ZPD) in facilitating second language acquisition. Building on this, Cummins’ contributions are examined in detail, particularly his distinction between Basic Interpersonal Communication Skills (BICS) and Cognitive Academic Language Proficiency (CALP), as well as the Thresholds Hypothesis. These concepts are used to explain the difficulties faced by minority learners when navigating between everyday communication and academic demands in English. The chapter also introduces translanguaging as a contemporary pedagogical approach that legitimises the use of multiple linguistic repertoires, enabling learners to draw on their home language as a cognitive and emotional resource. Together, these theories offer a multidimensional lens for analysing how Thai-speaking pupils negotiate their educational experiences, how language proficiency intersects with identity and motivation, and how schools can better respond to linguistic diversity. By situating the research within these theoretical perspectives, the chapter establishes a framework for interpreting the empirical findings that follow and for proposing more inclusive pedagogical practices.