In an EFL context, writing in English is often considered challenging for second language learners. Previous studies (Khumphee & Yodkamlue, 2017; Owu-Ewie & Williams, 2017; Richard & Renandya, 2002) suggest that a lack of sufficient cognitive and rhetorical skills for generating ideas and producing coherent compositions can be one of the challenges faced by learners. The transformation of education in this digital era means that learners ought to master their own learning path while dealing with many learning distractions. A ‘Genre-Based Self-Regulated Instruction’ (GBSRI) may therefore help language learners, particularly those with limited language proficiency, to accumulate competency in language, which in turn may encourage them to pursue independent writing and learning. This is due to GBSRI’s distinguishing features pertaining to genre-based writing instructions (Derewianka, 2003; Hyland, 2004; Macken-Horarik, 2002) and the practice of self-regulated learning (Schmitz & Wiese, 2006; Schunk & Zimmerman, 2007; Zimmerman, 2013). The objectives of this study were: (1) to examine the English writing ability of Thai undergraduate students by exploiting language features, text organization, and writing mechanics with a particular focus on two genres, namely: procedural writing and descriptive writing; and (2) to investigate Thai undergraduate students’ opinions as it related to GBRSI. The sample group in this study consisted of 32 Thai undergraduate students. For the purposes of the investigation, a one-group pre-test and post-test quasi-experimental design was utilized. The research instruments included: (1) pre-test and post-test paragraph writing, (2) a GBSRI questionnaire, and (3) semi-structured interviews. The results of the pre-test and post-test revealed that the ability of the participants’ paragraph writing was significantly improved subsequent to participating in GBSRI. Moreover, the qualitative data from the questionnaires and the semi-structured interviews indicated that most students expressed satisfaction with GBSRI and acknowledged its benefits. Furthermore, they stated that both their writing ability and self-regulation in learning had improved after participating in GBSRI, especially in explicit instruction, collaborative learning, and self-regulated writing activities. This study also showcases other considerations regarding the implementation of GBRI in different contexts.