This study presents a multi-faceted analysis of EFL learners’ voices in a Thai context, aimed at testing a hypothesis that the discourse of foreign, western-compiled textbooks project identities disconnected from EFL learners’ lived experiences, adversely affecting their meaning-making during discursive practices. I employ a multi-modal, multi-case study for data collection: 1) the use of two sets of materials in mini-course action research with two groups of learners — one group using published materials selected from New Headway Elementary Course (Soars & Soars, 2000) and the other using modified, parallel ‘Third Space’ materials; 2) audio- and video-recordings of classroom interactions and their transcriptions; 3) post-lesson and post-course questionnaires; 4) semi-structured interviews; and 5) video-based stimulated recall interviews. Drawing from Bakhtinian-Vygotskian sociocultural theories, I show through a microscopic analysis of learners’ interactions and utterances how dialogic relations between Other-discourse and Self-discourse shape learners’ meaning construction during their appropriation of mediating discourse for activities such as role-play. A macroscopic analysis of learners’ attitudinal voices based on the questionnaires and interviews is then provided for triangulation. The findings are 1) both groups have marked potential to infuse their contextual meanings into the Other-discourse of their materials for Self-representation; 2) ‘Third Space’ materials have more potential to enrich linguistic resources and opportunities for learners’ meaning-making and scaffolded learning than ‘Headway’ materials; 3) the majority of participants prefer the coexistence of voices and meanings between their culture and Other cultures as the mediating discourse for speaking activities, rather than the conventional models. The study thus supports the use of a dialogic framework for inclusion of cultural voices and representations in EFL materials design, and also offers other implications for pedagogy and future research.