Do you think a project manager client side can be hired as project manager contractor side?

The roles and responsibilities of Project Manager (client side/owner representative) are as follows. 

Project Planning and design

1.  Set a clear project goal and Objective

2.  Establish activities and detail budget

3.  Prepare Project schedule

Project Implementation

1.  Direct people individually and as project team

2.  Keep everyone connected with the project Informed

3.  Supervise the progress and work of project contractor

Project Control

1.  Review project progress every week and take action to move forward as planned

2.  Empower yourself and others on the project team

Project closing and Handover

1.  Please train people to take over the Project Function

2.  Handover the project as planned 

If we look the project manager form the contractor’s side, he/she will ensure project implementation and support the project manager (owner side) exactly in the same way to achieve the project goal. However, as an employee of contractor, he has to look after contractor’s interest in timely completion, submission of report and claim for work completed.

Yes, if the client has no objection to that.

I had been working with Government of Iraq as Assistant Resident Engineer (Design). Design work was complete and I was hired by the contractor on the same project with approval of the client. 

No, that is a confict of interset.