During the most recent CSS retreat, the teacher mentioned how thoughts are most embedded in the visual field, as opposed to the other ones (sensations, taste/smell, sound).
When I explored it for myself, I found that thought seems equally “embedded”, or rather laid on top of, each of the sensory fields. In my case, and I assume this is somewhat common, there is a layer of visual thought images put on top of each sensory field: There is a sound, and a faint image of a car is put on top of it. A taste, and an image of the nose/mouth/throat area and an apple. A sensation, and an image of an ankle with a mosquito bite.
This is the same for each sensory field.
What is different, is that with the visual field, visual thought images are put on top of visual perceptions. There is visual on top of visual, which can make it more difficult to differentiate the two.
One way to differentiate, which we did during the retreat, is to close the eyes and become aware of, for instance, the visual thought image of the body, particular body parts, and how they move in anticipation of a movement of the body, or to keep track of current movements of the body. Then, we can open the eyes and get a sense of how the visual thought images are placed on top of the visual perceptions. With some practice, they become quite distinct.