RaycastHit hit;
 Ray ray = new Ray(thisTransform.position + Vector3.up, Vector3.down);
if (Physics.Raycast(ray, out hit, 10f))
{
       float offset = thisTransform.position.y - hit.point.y;
       thisTransform.position = new Vector3(thisTransform.position.x, thisTransform.position.y - offset, thisTransform.position.z);
}