Can my employer cancel my work permit and visa extension without my presence?

Your best bet is go to labour department yourself then.

Your employment is controlled by the employer so they wont need power of attorney to cancel, not quite sure what happens if they dont have the book.

But if you no longer work there then they legally need to cancel work permit.

They legally need to give you the cancellation letter.

If you have the book then you can always go and cancel yourself, which is probably best bet

@Stuart ********

I'd think an agent (which could be anyone really) would be able to cancel a visa and work permit on behalf of an applicant as they're generally allowed to for extension purposes (I'm talking about visa types that don't require the physical presence of the applicant per se, which applies to non-B holders for instance)? Obviously the visa definitely needs to be canceled and the letter needs to have a future date on it, not the date on which it is canceled else the applicant would literally need to fly out or be prepared to get in a car or taxi bound for Cambodia to ensure they leave the country that day else they will be considered as an overstayer.