I have a job offer to work as an English teacher for a Government school. The company which offers the job told me that the school will not provide the documents to apply for a Non Immigrant Visa Type B and no working permits. They told me that they can organize an ED-Visa for me and that with the ED-Visa I am allowed to teach. Is this legal?

its illegal working whit ED VISA you need a work permit

its illegal working whit ED VISA you need a work permit

an if the police catch you you going to jail and paid fine i dont know how much and you canot come to thailand after that i think you go on Black list

As said you need the appropriate Visa and a Work Permit to work in Thailand.

You can't obtain a work permit with a non-immigrant ED visa. You need a work permit to work legally as a teacher.