1. Put beans into a large bowl; cover with water by 2 inches. Cover with plastic wrap. Let soak at room temperature 6 hours (or overnight). Drain; rinse.

2. Transfer beans to a medium saucepan; cover with cold water by 1 1/2 inches. Bring to a simmer. Cook, covered, until tender, about 25 minutes. Drain. Rinse with cold water, and let cool completely. Transfer to a bowl; cover with plastic wrap. Refrigerate 15 minutes.

3. Add carrots, onion, tomatoes, and parsley to beans; toss well. Whisk together vinegar, thyme, sugar, oil, and 1/2 teaspoon salt in a bowl until sugar has dissolved; season with pepper. Toss vinaigrette with bean mixture. Season with salt and pepper. Refrigerate in an airtight container (or store in a chilled cooler) until ready to serve, up to 4 hours.