Put a medium saucepan of water over high heat and bring to a boil and salt it. Rinse, trim, and chop the scallion, keeping the white and the green parts separate. Rinse and zest the lime using a zester or the fine side of a grater, avoiding the white pith. Rinse and trim the broccoli rabe and discard stems. Rinse and quarter the radishes.
Rinse the swiss chard in a colander to remove any grit. Separate the stems from the leaves by cutting the bunch at the point where the stems become leafy. Cut the stems into 1-inch pieces. Chop the leaves into bite-sized pieces.
Put a large skillet over medium heat and add 2 tablespoons vegetable oil. Once the oil is hot, add the curry paste and cook until fragrant, stirring constantly, about 30 seconds. Add the chard stems and scallion whites and cook for another minute; then add the broccoli rabe, radishes, chard leaves, and coconut milk and cover. Cook until slightly thickened and all veggies are tender, about 10 to 15 minutes and season with salt.
Put the noodles in a large bowl and cover them with 1 inch of boiling water. Let them sit for 5 minutes. Once tender, drain the noodles in a colander.
Rinse and pick the leaves from the cilantro. Add the lime zest and the juice of 1 half of the lime to the skillet and turn off heat. Cut the other half of the lime into wedges. To serve, put the noodles into a bowl and top with the vegetables and red curry sauce. Sprinkle with the scallion greens and cilantro and serve with the lime wedge.