Has anyone added a new "category of permitted work" to their existing work permit while staying in the same company? (Bangkok). Is it possible to do? Thanks in advance.

I want to ask a question relating to work permits(sorry not visa-related), I need to change my permitted category of work in the work permit, but my employer says that I have to quit the job and restart to do it, is it true? is the change of the permitted category of work not allowed? Has anyone done this before while staying in the same company?

I recently went through some newspaper article stating that you are allowed to work in any category of work(which is not stated in the permitted category of work in the work permit) as long as it is not a prohibited category of work. Thanks in advance.