In country medical extension, like many things, might depend largely on the IO one is at. Just got my 3rd 90 day ext at CNX. Walked in and out 😂. CM does have this ridiculously old form for the Dr to fill out. That plus medical report (done at same time as IO form) has really been all they cared about. Plus I have every C19 extension, haven't left Thailand in 3 years plus. Dr Chanakarn in CM is one of the world's best for arthroscopic surgeries, look him up! Understand your entry concerns, if you can, do get a 60 day tourist, extend 30, then try for medical in country.
Did you ask if they'll add the new 60 days onto your current expiration date? As opposed to 60 added on to application date. This morning I saw one report from promenada: adding 60 to application date.
nothing abnormal, one copy of passport first page and one copy of each extension. The covid extension forms, overstay forms etc can all be done in office.