Most embassies won’t let you apply for a new visa, if you already have a valid visa via MoFA. It needs to be canceled first. This is why individuals with METV have had to wait the six months before applying for a DTV. Only extensions made by immigration in Thailand can be canceled.
- the few applicants I have see were giving 15 day extensions, so that Immigration could then review the documents and supply decision. So there is a chance you pay, get a short extension while they decide and then learn the results in 2 weeks