Bring a large saucepan of salted water to a boil. Add potatoes and simmer until fork-tender, about 15 to 20 min. Meanwhile, toast pecans in a dry skillet over medium heat until fragrant. Set pecans aside and drain potatoes well.
Return potatoes to the saucepan and add the butter. Toss gently over low heat until butter is melted. Add salt, pepper, pecans, cranberries and thyme. Toss to combine and serve.