This action research was qualitatively conducted to investigate the factors enhancing the development of speaking skills of Thai EFL undergraduate students. A confidence factor was gradually developed during the 15 weeks of a regular listening and speaking course. A task-based pedagogical design provided opportunities for the course participants to speak in different situations, which helped to make ‘passive’ vocabulary ‘active’ and also expanded the English lexicon derived from varied speaking topics. Creativity of topics was considered to be a speaking strength, and errors in pronunciation and grammatical structure were categorized as weaknesses of the research findings. Suggestions for speaking improvement for EFL learners mainly covered listening skills, which included listening to music, watching movies, and frequent practice of listening and speaking skills from multimedia websites. The task-based learning design in this qualitative action research could be applied to promote a particular skill or integrated-skill pedagogy in EFL/ESL and other language learning contexts.