I’ve done what you told me but it’s not well either.

Now my minimumWorld is [0,0,0] and my MaximumWorld is [10,15,5]. It would be correct if my box was not rotated and translated.

if I call box.computeWorldMatrix(true) after the displacement and rotation of my box, my minimumWorld is [X: 1.0000000894069672 Y: 0 Z: -7.071067720651627] and my maximumWorld is [X: 11.606601625680923 Y: 15 Z: 3.5355338156223297] which fits to the red cube in my PG but which is not correct.

The boundingBox property is a axis-aligned bounding box, not an object aligned one, so it will only fit perfectly if the rotations are multiples of 90 degrees:

If you need to compute the object aligned box I’d bake the transform in the object and compute the BB again