Occam's Razor is a scientific principle that says we should not multiply causes beyond what is necessary to explain the effect. Since one Creator is sufficient to explain the effect, you would be unwarranted in going beyond the evidence to posit a plurality.
An example of such an argument would take this form: we have a set of models which does a good job of predicting various aspects of our experience (theories from physics, biology, psychology, etc.). Taken together these constitute a larger model of our overall experience, call it a World model. Elements (sub-models) of this World model which do not contribute to the precision or improve the accuracy of the model should be "cut away" with Occam's Razor. Given this foundation it can be seen that World models including God have an extra element that does not improve accuracy or precision.
A common response is that God can "simplify" the world model, for instance by providing a less complex explanation of the origin of species via creationism (i.e. even though we are adding the God-submodel we are removing a more complicated "evolution" model achieving a simpler theory). Concurrently, some over-simplify Ockham's principles as meaning "the easiest explanation must be correct" and argue that given the complexity of the Universe and the extremely small chance that it would have developed this way simply by a series of accidents, there must be a driving force that built the universe to be so complex. However, such arguments are problematic on at least two counts (aside from describing natural processes as "accidents").