Ideation, a phase of Design Thinking, merged with discussion activities is one innovative tool to encourage learners to speak and think critically towards a given topic. This research was conducted primarily to investigate the effects of ideation discussion activities in Design Thinking to speaking and critical thinking abilities of English as a Foreign Language (EFL) learners as well as their perception towards the concept. There were eight participants in the research study. Pre-test and post-test in speaking and critical thinking abilities, a set of survey forms, and participants' reflective essays were the instruments used in the study. Descriptive statistics, paired sample T-test, and content analysis were employed to measure the data gathered after the participants attended the 84-hour sessions of ideation discussion activities in Design Thinking course at Rajamangala University of Technology Lanna (RMUTL), Chiang Mai. Results revealed that these ideation discussion activities in Design Thinking were relevant to enhance EFL learners' speaking and critical thinking abilities. The level of agreement and the satisfaction of learners were high after they attended the sessions. It could be said that ideation discussion activities in Design Thinking could possibly enhance speaking and critical thinking abilities of EFL learners.