I needed a new dash cam and got one, off Lazada, which clipped over the rear view mirror, including a rear camera and some long wire. There is a smallish 40% size screen which can be on or off. Less than Bht 400.
It worked fine until I realised that every time I looked in the mirror, I was seeing what I should be looking at straight ahead, which I found very distracting. Also, the included rear view mirror was bluish and not so clear.
Lazada returns DO work.