Cook potatoes and beans according to package directions.
Meanwhile, put eggs in a saucepan, cover with cold water, and bring to a boil. Cover, remove from heat, and let stand 12 minutes. Drain, run eggs under cold water, and peel. Halve each lengthwise.
Blanch tomatoes in a pot of boiling water to soften, 30 seconds. Drain well.
Whisk together vinegar, mustard, salt, pepper, and thyme in a bowl. Gradually add oil, whisking until combined well.
Arrange potatoes, beans, tomatoes, eggs, tuna, and olives on a platter and drizzle dressing over top.
