In a small bowl whisk together 2 tablespoons of the soy sauce, vinegar, sugar, and ginger. Set aside.
Place a wonton wrapper on a work surface. Spoon about 1 teaspoon spinach and 1/2 teaspoon each carrot and corn in the center of the wrapper for triangles or on one side of the wrapper for rectangles. Drizzle vegetables with about 1/4 teaspoon of the remaining soy sauce.
Bring a large pot of water to boiling. Brush the edges of the wrapper with water. Fold the corners together for triangles or fold the edges together for rectangles. Pinch the edges to seal well. Repeat with remaining wrappers and filling ingredients. Gradually add the dumplings to the water using a slotted spoon. Boil the dumplings gently for 3 minutes. Remove from the water with a slotted spoon to a serving platter, draining the water off well. Serve warm with dipping sauce.