They want you to use an agent, then the agent gives them a backhander. We call it corruption, but if you want to get any thing done it is the easiest way.
Having said that, I have a retirement visa,bank account, driving licence, ID card, house book etc. All obtained without using an agent.
Like most things in thailand, it is easier to go through an agent.
And pay them in cash. Then they give a little backhander to various people who get involved. Welcome to thailand, where there is no corruption honestly.
Thailand has many laws. Many of them are broken regularly (particularly driving laws). However when it comes to foreigners and overstays, they are strict. It's a shame the UK can't take the same aproach and deport and ban all illegal immigrants.