1. Shell the shrimp. Devein them by making a shalIow incision down their backs with a small, sharp knife and lifting out the black or white intestinal vein with the point of the knife. Wash the shrimp under cold running water and set them aside on paper towels to drain.
2. Put the chilies and onions through the finest blade of a meat grinder, or puree them in the jar of an electric blender. Transfer the puree to a heavy 2- to 3-quart saucepan and stir in the lemon grass, basil, turmeric, laos powder and 1 cup of water. Bring to a boil over high heat, reduce the heat to low and simmer uncovered for 5 minutes.
3. Stir in the zucchini and continue cooking for 5 or 6 minutes longer, or until the squash shows only the slightest resistance when pierced with the point of a small knife. Add the coconut top milk and the shrimp and, stirring frequently, cook for 4 or 5 minutes until the shrimp are firm and pink.
4. Do not allow the liquid to boil or it will curdle. Remove the pan from the heat, stir in the lemon juice and salt and taste for seasoning. Serve at once from a heated bowl, accompanied if you like by hot boiled rice.
