yes, you can just go there without any appointment. We took with us only original documents + photos, and at immigration we asked what copies do we need. Copies you can make on the ground floor. And they also will give you TM7 and two more forms to fill in.
I showed only TM30 slip. No other proofs. But I think it depends on country. So better to take everything you have with you and ask at place what they need.
So, today I’ve got an extension. Ukrainian passport. Will write a separate post about it. If to be short, extensions due to Covid 19 are at Promenada. Needed only one copy of passport pages, embassy letter, all forms that I get at immigration, TM30 slip, one photo, 1900 batt. It took us two hours to apply all the docs and to get extensions until October 26.
Could you help me, please. Who knows the list of documents needed for visa extension with embassy letter at Chiangmai immigration? Can’t find this information.