My hair is very sun blonde

no shampoo is gonna make your hair thinner ! if you do want it thinned out then get some thinning scissors..they wont take the lengh off,they are also good for split ends.

I like Pantene's Smooth and Silky shampoo and conditioner. It leaves your hair more tamed, and it won't look bushy or too thick (if there is such a thing as too thick).

Garnier Frutise (I don't know if that's exactly how you spell it)

I use Halo Smoothing shampoo and conditioner. My hair is thick and blonde as well and it works so well. My hair sometimes gets out of control and whatever is in this shampoo really helps tame it.