I wouldn't be so sure, I watched a interview with immigration Minister and some YouTuber, he said when you extend, immigration may ask to see your work portfolio, I assume if you have a muay Thai or cooking course and you are in and out of Thailand they "may" question how you are completing the requirements of the course, i have also read on Reddit some immigration officers are asking questions like why did you apply in Taiwan/Vietnam and what's your purpose for coming to Thailand becides having an dtv visa ...