"You will need some time remaining on your “admitted to” stamp. Bangkok Immigration requires at least 15 days, Chiang Mai requires at least 21 days. Contact your local immigration office for more information."
If you applied for it on Monday, you applied for the old "60 day extension of stay based on unable to travel due to COVID-19" that is no longer being sold. I never heard of any rejections for this extension of stay, so you should be fine.