Until you can define the nature of what a thought is, you can't make such assumptions about our ability to choose a thought.
Firstly, wow! You really are shameless in your gross double standards. The central concept of your whole appraoch is 'free will' which you have been completely unable to define.
Secondly, the definition of free will logically matters to your 'argument' in order to explain why it can't be physical and how it can exist in some non-physical way. However, the exact nature of a thought is unimportant to the idea that we can't choose our thoughts. The very act of making a conscious choice requires us to think about it, which leads to the infinite regress.
Choose not to think about a red circle and let us know how well you did.
You get into this infinite regress by trying to make a conscious thought fit the same type of determinism we get in machines, but our conscious awareness can't be replicated by any machine type determinism.
There is only one type of determinism.
And it is totally irrelevant to this point.