Thought or intention is always karma? "Chethanaham bikkawe kamman wadami". 


  Dear Bikkhus, I introduce thought as karma. It is after having thought
  that we engage in action physically, verbally and mentally. (
  Nibbedhika sutraya)


My question is simple. Does thought or intention alone become karma? Or does it need to have certain characteristics (Sorry if this word is inappropriate) for it to become Karma? If intention alone is karma whether we engage in action in though, word or deed what is the point of good deed? 

 Can we just "think" that we are helping the poor and have good karma? Can we "think" that we are giving dhana to monks and have good karma? In the context of good karma, can we just have good intentions and thoughts of good deeds and get the same karma that we get from physically engaging in such activities?
Thought is what decides Karma. Same action with different motivation or volition can be bad or good depending on the motivation or volition. That is volition is what becomes Karma. 

If you follow though with your intentions then this can lead to rebirth linking Karma. If you don't it will be weaker Karma. 

If you have the volition but not the means to follow through then it will be a weak Karma as discussed above. 

Volition bears fruit based on the root and level of mental lethargy or whether you or someone else has to prompt or motivate you to do something. If you have the thoughts but not the desire to do it then the root are missing or very weak hence there is unlikely to be Karmic results. If there is lethargy but there is genuine desire, the roots weak but present hence will have diminished Karmic results. More than the thoughts, imagination of doing something, visualisation of doing something, what counts is motivation or volition or desire to do the thing, though such thoughts could lead to desire or motivation or volition to act. As discussed above all factors may not align to successfully follow through nevertheless karma is created but at different intensities of potential results.