i'd just do exemption yes - my friends have used the fast track no problems, i wouldn't chance it going it alone lol, at least if questioned you have someone there with you who is at immigration every day.
The cambodia place i used was first class visa runs pattaya but they have discontinued their service now, quickly searched and these guys look legit:
land border, the bus goes from pattaya thai to the border which is 4 hour journey - 10 hour round trip as 2 breaks. You get 45 days which you can then extend 30 so 75 total.