Ensure your company issue you a return flight to work each time before you arrive here.
If you ever get questioned at immigration explain you work a 4 weeks on and 4 off rotation in X country. You can have your work contract available with you incase you do get questioned in depth.
You also qualify for a DTV as you are a contractor.
Some have said get a 2nd passport but that wont make any difference at all. I have 2 passports and if I leave a country on one of them and arrive on the other I get asked "do i have another passport?" and then I have to show the passport I left the country on.