This research offers a critical exploration of cultural depictions and implicit power structures embedded within the Student’s Book SPARK 2 (2008), an EFL textbook widely adopted in Thai lower secondary education. Applying Critical Content Analysis (CCA) as the core methodology, the study investigates how cultural narratives—particularly those related to Western and non-Western societies—are constructed through both textual and visual modes, with a focus on whether Thai cultural elements are meaningfully represented. The analysis reveals a strong Western-oriented bias, prominently featuring American, British, and other Anglophone cultural contexts, while representations of Thai culture are minimal or absent. Beyond the explicit cultural references, the textbook communicates subtle ideological themes related to obedience, environmental responsibility, and social norms, reflecting a form of "hidden curriculum" that shapes students’ perceptions of identity, authority, and global cultural hierarchies. Furthermore, the emphasis on individual action in addressing global challenges, alongside the prioritization of Western literary and cultural models, reinforces patterns of cultural and linguistic dominance. The findings underscore the necessity of evaluating EFL textbooks not only for their pedagogical and linguistic value but also for the cultural and ideological frameworks they promote. The study advocates for the inclusion of more diverse, inclusive, and locally resonant cultural perspectives to enhance students’ intercultural communicative competence and support more equitable English language education in Thailand’s culturally pluralistic society.