Place potatoes in a medium or large saucepan and pour over enough water to cover by about 2 inches. Set pan over high heat and bring water to a boil. Boil 8 minutes, until potatoes are fork tender.
Drain and transfer potatoes to a large bowl. While potatoes are still warm, add olives, tomatoes, onion, olive oil, vinegar, and thyme and toss to combine. Season, to taste, with salt and black pepper.