Sheikh: I said a word and my friend laughed; have I thereby committed an act of disbelief?

Mere laughter does not cause apostasy (riddah), for apostasy is the embracing of disbelief (kufr) with an open heart. Whoever enters Islam with certainty does not exit it except with certainty. Therefore, one must repel the whisperings (waswasah) concerning this matter and distance themselves from pathological doubt and confusion.