Keratosis pilaris causing many countless ingrown hairs, laser hair removal an option to kill problem at root?

Yes it is. But it may take several treatments over years because many follicles will be in the telogen phase (sleep phase) and is is often combined with microdermabrasion or other exfoliative treatments.
Before you try that. I would recommend trying different topical products, then laser treatment. Every person will react different so give each product/method time so that you are able to see which works best for you :].