Can I convert a tourist visa to a marriage visa in Thailand, or do I need to apply from a neighboring country?

I posted about if it's possible to convert a tourist visa to a marriage visa the other day. At the time I was posting as a sanity check and didn't have time to share the details. I'm dealing with another round of comical fuckery from immigration with its "up to me" attitude and widespread lack of professionalism. I just don't understand how things can function like this, but whatev.

CR told me last week they could not do marriage visa and we had to go to Maisai. They gave me a pink printout with the requirements- it is incomplete with things like "proof of 400k for at least 2 months"- but this is not enough information. A stamped statement is not enough. Apparently your book needs a special stamp AND they require a letter from the bank. The person who prepared the pink sheet and the person who approved it should both be harvesting rice not working in administration... Anyway- so we go to Maisai.

Maisai says I cannot convert a tourist visa to a marriage visa and I must go to a neighbouring country and get a new stamp. Then when I wanted to do the 30 day extension they started requesting more and more documents I've never been asked for until I got fed up and left. Basically the lady had decided she didn't want to help me and it's better to retreat than let the bully enjoy themselves. For reference- she wanted a printout of my TM30, printout of my lease, printout of my wife's ID and housebook...

So we go back to CR to get the 30 day and ask for clarification on the visa issue. They gave me multiple pieces of conflicting information and called Maisai to ask them why they didn't help.

1) they said that the proper visa to get a stamp that convert to marriage visa IS NOT AVAILABLE via the website. I don't know if this is true- but two staff stood and solemnly swore you must have a visa from a physical embassy.

2) they also said that if I had the proper visa they would have been (more on this in a second) happy to do my marriage visa- but then why the fuck did they tell me to go to Maisai to start with?

3) when I first came to Thailand I did an education visa. Yes yes corruption/abuse/etc etc. I did not make the policies or abuse the system- so punishing me is fucking retarded. Not ONLY have they treated me like a sex offender because of this stamp for 2 years they have OPENED UP the rules allowing for longer education visas. It's fucking absurd.

3a) so when they called Maisai and talked to the IO who gave us trouble she said it was because of the ed-stamp

3b) they then claimed that the only way to fix it is to go to... Crap the name is eluding me- whatever the immigration office is that people say to go to when you don't have the 400k or you have some other issue... Suvonicape? Something like that. This was interesting because I had always thought it was just a shady office that was willing to do under the table stuff rather than somewhere other immigration offices would try to refer you to.

Anyway the whole thing is just embarrassing. I'm willing to jump through hoops, but I can't wrap my head around them not being capable of giving a straight answer as to what those hoops are.

I am torn on whether I should just continue to follow the breadcrumbs like I am in Lord of the Rings or just hire an agent.