What are the requirements for obtaining an ED visa in Thailand for an internship, and can I convert my METV?

Dear Group, I need your expertise in the following case. Thank you already in advance for your help.

I have been travelling since beginning of the year in Southeast Asia. However, I spent most of the time (around 60 days) in Thailand on visa exempt stamps.

Now I would like to stay longer here and I am searching for a job. By now, I was only offered with an internship, which I would like to do - to get settled here. But now the problem comes.

The company offering the internship says I need from my university an official letter that I have to do a mandatory internship. My uni can only provide a letter that an internship is beneficial for my education but it is not a must. So I went back to the company and they said they think it is a requirement from Thai officials for the visa, I cannot get one without. Is that right?

Provided that it also works out and I can apply for the ED visa, I can do this from any neighboring country, right? I have a German passport. Is there any risk for this?

Right now I am home and I need to reenter Thailand. I would like to get the METV so that I can stay longer on tourist visa if internship doesnt work. Could I go then with my METV to a neighboring country and apply for the additional ED visa or how is the process? Do I have to cancel my current one? What happens when I cancel my METV but dont get the ED at the consulate? Can I convert METV to ED here in Thailand?

Also what would happen if I get a real job. Can I convert either the METV or the ED in Thailand or do I have to go abroad?

Thanks guys! Hope the info provided above is ok, otherwise, please let me know what else you need.