user7290: 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?  

user6994: There is karma that is intention (an omnipresent mental factor) and karma that is intended actions.
Intended actions are defined by Je Tsongkhapa as:

The actions of body and speech that are motivated by that intention.


Afflictions such as anger, jealousy, covetousness, and so forth are not the intention mental factor - but have their own entity as mental factors - therefore they are not karma. Anger manifests from a seed of anger and that seed is not a karmic seed, because it was "deposited" by a previous instance of anger (not by a previous karma - that is intention or intended action).
However, some qualify the afflictions as 'karmic path' or 'paths of actions' because they are likely to lead one to engage in negative actions (karma).

user-1: Bhikkhu P. A. Payutto writes:

But according to the teachings of Buddhism, all actions and
  speech, all thoughts, no matter how fleeting, and the responses
  of the mind to sensations received through eye, ear, nose,
  tongue, body, and mind, without exception, contain elements of
  intention. Intention is thus the mind’s volitional choosing of objects
  of awareness; it is the factor which leads the mind to turn
  towards, or be repelled from, various objects of awareness, or
  to proceed in any particular direction; it is the guide or the governor
  of how the mind responds to stimuli; it is the force which
  plans and organizes the movements of the mind, and ultimately
  it is that which determines the states experienced by the mind.
One instance of intention is one instance of kamma. When there
  is kamma there is immediate result. Even just one little thought,
  although not particularly important, is nevertheless not void of
  consequence. It will be at the least a “tiny speck” of kamma,
  added to the stream of conditions which shape mental activity.
  With repeated practice, through repeated proliferation by the
  mind, or through expression as external activity, the result becomes
  stronger in the form of character traits, physical features
  or repercussions from external sources.
-- Good, Evil and Beyond: Kamma in the Buddha's teachings

As there are physical movements that are devoid of intention (e.g. convulsions), some mental images might be understood to surface unintentionally. While the quote above asserts all thoughts to have intention, it can be argued if these are understood to be karma or not. Dreams would be in this gray area, I think.
But, while awake, any sophisticated thought, anything more than a flash of an image or a sound or taste or smell, any and all imagination containing full sentences, dialogues and motions, etc, have an active element in them which nurtures and develops them: underneath, there's the intention to imagine these things, and these imaginations are actions -- which is the meaning of karma in Buddhism.

7290: <p>This question is about a very specific situation, but there might hopefully be a more general answer. </p>

<p>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. </p>

<p>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. </p>

<p>But the question is, does the thoughts in themselves create bad karma?  </p>
 6994: <p>There is karma that is intention (an omnipresent mental factor) and karma that is intended actions.</p>

<p>Intended actions are defined by Je Tsongkhapa as:</p>

<blockquote>
  <p>The actions of body and speech that are motivated by that intention.</p>
</blockquote>

<p><br>
Afflictions such as anger, jealousy, covetousness, and so forth are not the intention mental factor - but have their own entity as mental factors - therefore they are not karma. Anger manifests from a seed of anger and that seed is not a karmic seed, because it was "deposited" by a previous instance of anger (not by a previous karma - that is intention or intended action).</p>

<p>However, some qualify the afflictions as 'karmic path' or 'paths of actions' because they are likely to lead one to engage in negative actions (karma).</p>
 -1: <p>Bhikkhu P. A. Payutto writes:</p>

<blockquote>
  <p>But according to the teachings of Buddhism, all actions and
  speech, all thoughts, no matter how fleeting, and the responses
  of the mind to sensations received through eye, ear, nose,
  tongue, body, and mind, without exception, contain elements of
  intention. Intention is thus the mind’s volitional choosing of objects
  of awareness; it is the factor which leads the mind to turn
  towards, or be repelled from, various objects of awareness, or
  to proceed in any particular direction; it is the guide or the governor
  of how the mind responds to stimuli; it is the force which
  plans and organizes the movements of the mind, and ultimately
  it is that which determines the states experienced by the mind.</p>
  
  <p>One instance of intention is one instance of kamma. When there
  is kamma there is immediate result. Even just one little thought,
  although not particularly important, is nevertheless not void of
  consequence. It will be at the least a “tiny speck” of kamma,
  added to the stream of conditions which shape mental activity.
  With repeated practice, through repeated proliferation by the
  mind, or through expression as external activity, the result becomes
  stronger in the form of character traits, physical features
  or repercussions from external sources.</p>
  
  <p>-- <a href="http://www.buddhanet.net/pdf_file/good_evil_beyond.pdf" rel="nofollow">Good, Evil and Beyond: Kamma in the Buddha's teachings</a></p>
</blockquote>

<p>As there are physical movements that are devoid of intention (e.g. convulsions), some mental images might be understood to surface unintentionally. While the quote above asserts all thoughts to have intention, it can be argued if these are understood to be karma or not. Dreams would be in this gray area, I think.</p>

<p>But, while awake, any sophisticated thought, anything more than a flash of an image or a sound or taste or smell, any and all imagination containing full sentences, dialogues and motions, etc, have an active element in them which nurtures and develops them: underneath, there's the intention to imagine these things, and these imaginations are actions -- which is the meaning of karma in Buddhism.</p>
