My philosophy to any great dish is to find the basic flavor that you are going for, then build on that. In the case of a good Thai soup, that flavor would be yellow curry.
First, create a Thai curry sauce.
Second, thin it out with chicken stock.
Third, sautee appropriate vegetables and shrimp separately in a skillet.
Fourth, mix all ingredients and heat together.
Fifth, garnish with cilantro and cashews.
My suggestion for a few good soup vegetables: halved grape tomatoes, sliced mushrooms, fresh spinach, cubed onions, cubed potatoes, julienned carrots, and sliced red bell peppers.