Vocabulary development in primary education requires more than increasing the number of words students recognize; learners also need to clarify word meanings, establish lexical relationships, and use vocabulary productively. This study identifies classroom needs in theme-based vocabulary instruction for Grade 3 students and develops a pedagogical framework grounded in lexical-semantic theory, curriculum requirements, textbook tasks, and empirical needs analysis. The study draws on data from 218 Grade 3 students and 15 teachers at three primary schools in Thai Nguyen Province, Vietnam. Student performance was uneven, with 47.7% scoring below 7 on a 10-point vocabulary-expansion assessment. Teacher responses also indicated limited use of instructional supports specifically targeting lexical recognition, guided retrieval, and productive activation. In response, a four-component framework is proposed: lexical recognition, semantic clarification, lexical systematization, and lexical activation. Corresponding measures include guided reading and observation, semantic-feature comparison, associative and syntagmatic organization, and experience-based vocabulary use. Classroom illustrations show how these measures can be integrated into Grade 3 Vietnamese textbook tasks without altering curricular content. The framework offers a structured approach for moving vocabulary instruction from word accumulation toward meaningful lexical organization and communicative use.