Which hair cut is best suited for thin straight hair?
Ok, first off, DO NOT LAYER YOUR HAIR.
You have straight hair. When you said "thin" hair, do you mean it's thinning on scalp area or the hair is fine in texture? Big difference between the two.
I looked at your profile but I don't know if the picture is you. If it is, you don't have thin hair. You may have fine hair.
It you have straight, thin or fine hair, having it a little long on top and parting it on a side angle, will help camouflage the scalp a bit and it makes hair look fuller...thicker.
There is an option that is super fun if you are willing to try it. A pixie cut and going blonde or platinum. In doing so, you are colouring the hair to a pale colour, next to the scalp, this gives less contrast. You won't see the scalp through your hair as much.
When hair is thin, it's usually stringy when you grow it long. So I would not recommend that you grow it longer than a chin length bob.
Michelle Williams has super fine and thin hair. Her hair got thinner after she had her child. So, she went super short. Here is one hairstyle at different stages of it growing out. She tried the longer look again but has since cut it all off again. It's what best suits this hair type.