Do thoughts create karma?

This question is about a very specific situation, but there might hopefully be a more general answer. We've had conflicts at work, to the extent that we had to get a psychologist help us! There are many reasons for the conflicts, but for me the problem is that many of my co-workers are kind of lazy, not very competent and spend their time not doing their job but knitting, chit-chatting, complaining about everything etc. This situation leads to conflict and I have spent too much time being annoyed and tried to change the situation. Still, I sometimes think negative thoughts about these people. When I catch myself thinking negative ("lazy, incompetent people") I try to take a look at myself and see what causes the thoughts and what I really am thinking. This strategy also helps me to not take it out on them. But the question is, does the thoughts in themselves create bad karma?