[Visa extension]
For your information I was able to extend (first extension) my visa for one month (until 26th of October) without having any letter from my embassy nor medical certificate. I went to the immigration service in Chiang Mai - Promenada, with the usual requested documents for extension plus the TM30 (notification form of residence) and paid the 1,900 THB. I am French nationality but I guess it doesn't matter.
Good luck everyone 🍀