Lightly spoon flour into dry measuring cups; level with a knife. Combine flour and salt in a medium bowl. Combine water and eggs in a bowl; stir well with a whisk. Add to flour mixture, stirring with a whisk until almost smooth. Let stand at room temperature 30 minutes.
While crêpe batter stands, heat oil in a large saucepan over medium-high heat. Add crushed red pepper and garlic; sauté 1 minute. Add thyme and tomatoes; reduce heat, and simmer, uncovered, 5 minutes or until sauce is thick and reduced to 2 cups. Remove sauce from heat, and set aside.
Steam Swiss chard leaves, covered, about 30 seconds or until leaves wilt. Drain and pat leaves dry with paper towels. Cut each leaf in half lengthwise; set aside.
Combine 3 tablespoons Parmesan cheese, mozzarella cheese, and next 4 ingredients in a bowl; stir well, and set aside.
Place a 10-inch crêpe pan or nonstick skillet coated with cooking spray over medium-high heat until hot. Remove pan from heat. Pour 1/3 cup batter into pan; quickly tilt pan in all directions so batter covers pan with a thin film. Cook about 1 minute. Carefully lift edge of crêpe with a spatula to test for doneness. The crêpe is ready to turn when it can be shaken loose from the pan and the underside is lightly browned. Turn crêpe over, and cook 15 to 30 seconds. Place crêpe on a wire rack; cool. Repeat procedure until all of the batter is used, stirring the batter before making each crêpe. Stack crêpes between single layers of wax paper or paper towels to prevent sticking.
Preheat oven to 350°.
Spoon 1 1/2 cups tomato sauce in bottom of a 13 x 9-inch baking dish. Place half of a Swiss chard leaf on each of 8 crêpes; top each with a half slice of prosciutto. Spoon about 1/3 cup ricotta mixture down center of each crêpe. Fold over edges, and place, seam sides down, over tomato sauce in dish. Spoon remaining 1/2 cup tomato sauce evenly over crêpes, and sprinkle with remaining Parmesan cheese. Bake at 350°, uncovered, for 30 minutes or until sauce is bubbly.