With a working visa....is there any problem to leave Thailand spontaneous for example for holidays? Or is there a need to inform the government, before leaving the country or something like that?
TLDR : Answer Summary
If you hold a single entry working visa and plan to leave Thailand for holidays, you will need to obtain a re-entry permit to ensure that you can return without issues. This can be obtained from immigration or at the airport before you depart. However, if you have a multi-entry visa, no re-entry permit is necessary.