I say, and with God's success: His prayer is invalidated, not the ablution; because it is a condition for the praying person whose ablution is nullified by laughter to be either in a state of ritual purity or to have performed 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.