Cognitive control is a mental construct thought to be important in most cognitive tasks, including second language learning. Its functions are believed by many scholars to be mainly domain-general, with some transferability across linguistic and non-linguistic domains. Our study aims to investigate to what extent the domain-generality claim of working memory (WM) between the visual and verbal domains is true in Thai adults aged 18-36 years old. Subjects maintain and manipulate contents in the computerized WM tasks in the verbal (English, Thai, and Mixed Thai-English) and visual (kaleidoscope) domains. We hypothesized that (1) there are correlations in the WM manipulation effect of behavioral performances within the verbal domain, and (2) there are correlations in the WM manipulation effect of behavioral performances between the verbal and visual domains. Behavioral results (hit rates and reaction times) indicate significant correlations among the WM manipulation effect among the three language tasks, but not between the language and the visual tasks. Implications include that cognitive training and improvement are possible, but only within the domain. The manipulation effect can be trained across different languages using linguistic tasks, but visual tasks may not produce the desired manipulation effect in the verbal tasks. Cognitive trainings that use both linguistics and non-linguistic tasks simultaneously to train the students' WM are recommended to achieve the manipulation effect in the language domain.