Currently, there are about ten Vietnamese textbooks for foreigners selected as teaching materials in educational institutions across the country. However, the lack of cultural annotations in these textbooks has created many difficulties for both teachers and learners. In response to this issue, the paper proposes adding knowledge about Vietnamese culture, particularly communication culture, to improve the textbooks to better suit learners. This addition will support learners in cultural integration and development of Vietnamese language skills, helping educational institutions achieve their training objectives for teaching Vietnamese to foreigners.