Ground almonds can definately be used as a soups or stews thickener. In fact, almonds were often used to add texture and flavor to a 'white' soup and are still used for this purpose in some traditional dishes. This delicate flavor of almonds blends particularly well with fish and chicken.
However, compared to other starchy ingredients such as flour, ground almonds do not thicken soups in the same way. Flour will blend into the liquid to make a thick, smooth sauce but ground almonds add body, texture, flavor and richness. When using ground almonds, it is best to start off with a small amount and increase more, a little at a time, if necessary.
** Asian Recipes