Sorry for the incomplete information, below is the info:
I am on Closed workpermit (on LMO under skilled labour category) currently working in Ontario province. As you have mentioned that I should apply for PR after 2yrs of stay in Canada and as my work permit will expire on May 31st 2013 so wanted to know when can I apply for work permit extension
Also I will be applying for PR on my own.
Your employer will have to apply for a new LMO for you to be able to extend your work permit. Because it takes some time, they could start doing it in the beginning of 2013.