@Erin *****
totally depends on what border you to to and if you use a company to take to there and back or do it yourself. The fee the company charges already has the "bend the rule so you don't have to stay a day in cambodia" figured into the price. 😛
Poipet is the worst border right now to bounce at and I don't know any services that use it.
Good Luck with it, don't forget you need an approved thai pass to get back in (but again most services that take you to the border have that and the mandatory 10K USD of insurance figured in to the cost as well)