A very relevant topic Megadp! I will try to give my opinion, which may or may not be entirely right. Even I would love to know more about this. According to me the difference between the intention and fantasy is belief. Though the difference is very very thin. I feel when you think or imagine something, and you believe that it is possible, you are setting an intention. For instance, you are imagining earning quite a good amount of money and you believe that its possible for you, you are setting an intention. When you are imagining something but you do not believe that its possible, you are fantasizing. For instance you imagine yourself growing wings and flying on your own, but you do not believe in it and you think its impractical. Thats a fantasy for you.
I think fantasy can become an intention if you truly believe in its possibility. Also, the decision about which thought is fantasy and which is an intention can be subjective as it differs from person to person. One person may believe that walking on water is possible, and hence he/she succeeds in doing that (there are many people in the past who have done that actually). Another person may never believe that he/she can ever walk on water, and so, even if they fantasize about it, they'll never be able to do it in reality.
I think great miracles happen when fantasies turn into intentions, and those intentions turn into manifestations
