If you believe you can tell what a person is good for/incapable of, or is liable/unlikely to do, simply by looking at them and determining their "race", then you are engaging in racism.
Therefore, if you are faced with two job applicants and you require someone with math skills, and both applicants have the same math credentials but you hire the Asian applicant because you figure "Well, he's Asian and they're always good at math" - then you have engaged in racism.
It's not that you're thinking something bad or insulting about the applicant. It is that you are assuming, because of what you believe about his "race," that he's good for some particular thing. The belief that his "race" determines what he can or can't do IS WHAT RACISM IS. It would be the same as if you had decided not to hire a white guy as a dance instructor even though his credentials are the equal of the other applicants "because white folks can't dance a lick."
So yes, you can be racist towards Asian people, and that can be either because you think they're smart just because their Asian, or because you think the guys are gay and the girls are gold-diggers just because they're Asian. Any of those things are equally racist, because they all draw conclusions about a person simply on the basis of their "race".