Been here on a retirement visa for over 20 years. Most of that time I did my own paperwork and every time, I have found Immigration to be friendly and pleasant. Sometimes, I would have to go with some changes and get a different photo or form to fill out - I was living in an outer province - I had to mail in my 90 day report.
I am now in a larger province where there are visa agents who fill out all the paperwork and for a nominal fee, they make the entire process very easy and fast.
I do meet the legal requirements and keep the 800,000 baht in the bank -
It probably appears very confusing but if you qualify, it is not so bad and if you use an agent, it is very easy.