The batter squares to bunt and makes contact with the pitch. The ball bounces in front of home plate. The ball then bounces up and hits the bat again. Both feet of the batter are still in the box. Is is a foul ball? Is the batter out?
While a bounced ball could never be a called strike, a batter is allowed to swing at such pitches, so the ball is in play regardless of the bounce.
Since the ball strikes the bat twice and the batter is still in the box, this would be under 5.09(a)(7)
5.09(a) A batter is out when: ...
(7) His fair ball touches him before touching a fielder. If the batter is in a legal position in the batter’s box, see Rule 5.04(b)(5), and, in the umpire’s judgment, there was no intention to interfere with the course of the ball, a batted ball that strikes the batter or his bat shall be ruled a foul ball;
Unintentional contact while in the batters box: foul ball.