I say, and with God's success: His ablution is not invalidated; because it is a condition for the one praying whose ablution is invalidated by laughter that he be awake. Even if he sleeps during the prayer in any position, his laughter does not invalidate the ablution. Refer to: Sharh al-Wiqayah, 2: 33-34, and Tabyeen al-Haqaiq, 1/ 11, and Fath Bab al-Inayah, 1/ 68, and al-Ikhtiyar, 1/16-17, and Mukhtalif al-Riwayah, p.344-345, and God knows best.