Ludwig von Mises thought that thinking and acting were inseparable. Take a look at his book, Human Action, pp. 24-25 and 177.
David Gordon believes that thinking is an action because it is purposeful behavior. Take a look at his book, Introduction to Economic Reasoning, pp. 18-20.
I think that Rothbard, Mises, and Gordon would agree that reason is the precondition for thinking while knowledge or ideas themselves are the product of thinking. If thinking is considered an action, then, it would employ the scarce resource of the person’s brain.