Drain the soaked lentils and cover with fresh water. Bring to a boil and cook about 30 minutes, or until the lentils are tender. Heat the oil in a large saute pan and cook the shallots and garlic until just tender. Add the squash and cook for a few minutes. Add the tomatoes and thyme, and cook for 10 minutes. Add the lentils and cook for 10 more minutes or until all the ingredients are tender. Add the chestnuts and warm through. Serve with crusty bread.