Such anecdote are very rare, I'm sure you know it. There is usually more to these stories. p.s: You could go to Savannakhet to get Non-O based on marriage pre-covid without the 400k financial requirement. It was even possible in Penang for a while. This particular requirement is there so that some can profit from it (agent, officer, etc). It doesn't make a whole lot of sense. It's different from volunteer work where not going defeat the purpose of it, or not going to school on ed visa. It would be the equivalent of having a marriage visa without being legally married (not having marriage certificate).
You implied that the stamp and the visa were not real or fake, its real and legit. Maybe we just dont have the same definition of what is a scam, fake and not legit.
For marriage visa you need the marriage certificate, so yes you need to be married. You first need the affidavit from your embassy, then having it translated and certified by ministry of foreign affair (there is one in Bangkok and Chiang Mai), then you go to district office to get married and get marriage certificate. The whole process is no more then a week. After that to get the marriage visa you need to have had 400k baht in the bank for months or proof of 40k baht per month income. If you do not met the financial requirement, you can use an agent, they still do marriage visa.
Doing volunteer or ed visa the "normal way" imply that you will need to volunteer or go to school. If it's something that you want then do it the "normal way".
Yes, a visa obtained with an agent is legit, as long as it's a real agent and not a scam. A real agent will provide the payment slip, real stamp done by real immigration officer, and everything will be registered as if it was done without an agent. But yes, you do pay more to avoid one of the requirement. To me, it's the equivalent of black market lotto tickets in Thailand. If you win, you get paid, many buy such lotto tickets including cops. Is it legal? Not technically, but it's legit in the sense that they are delivering exactly what they are claiming to, and every stamps, etc, are all delivered the way it would the other way. Same with lotto tickets... you get paid with real Thai baht if you win, not fake ones.
1.9k is when you do actual volunteer work. 35k is when you are suppose to but stay home. People use agent to avoid volunteering or going to school, but still be on that visa. It is not possible anymore to do so.
55k is never legit, it's way too expensive. But the way you worded it is "every agent and visa obtain with agent is bogus", which is factually incorrect. A lot of people are married but they don't have the 400k in bank, this is why they use an agent to get marriage visa. To get a marriage visa with an agent, you need to met every requirement except the financial one (this is why many use an agent). So the marriage certificate need to be valid and everything else.
Get married, even if it's not a good reason to do so. It's the only way for you to stay long term in Thailand atm if you are not over 50 (retirement). I've been with my Thai GF for 6 years, we will get married soon. There was a time where you could get education visa and not go to class, but it haven't been possible for maybe 2 years (immigration will properly test you Thai skill every 3 months). Months ago they also discontinued volunteer visa with agent, so if you want one you need to volunteer for real. So any long term visa right now except marriage mean that you need to give a lot of your time for a foundation or at school.
Do not listen to Bobby, he does not speak from experience. To answer your question, all sort of visas obtained with agent (volunteer, education visa, marriage, etc), are legit. The stamps are all done the same way if you had not use an agent. BUT... right now volunteer and education visa are NOT available with an agent. If an agent offer you such visas it's a scam. Marriage visa is the only visa one that agent can do atm (if you don't meet the 400k requirement, if you do, do it yourself).
Volunteer visa with agent has been discontinued months ago, same with ed visa, the only available long term visa with agent atm is marriage visa (if you cant meet the 400k bath requirement, you use an agent). Also, there is no such thing as a "visa shop". A proper agent has an office that you can go in and visit, and will make your visa extremely fast after they receive your passport. "Delayed", even by a week, is also a red sign.
Two things are factually incorrect about your post. 1) The cost for a volunteer visa with an agent was never 50k+, it was always around 35k baht. 2) The visas obtained with an agent is not bogus, it's legit, but ofc it's true that plenty of agents are fake and will steal your money. As for right now, the only long term visa available with an agent is marriage visa. Volunteer and Ed visa is not available with agent atm. If someone offer one, it's fake 100%.