If people cry at weddings why should they not laugh at funerals? If the person who has died made them laugh when he/she was alive, then laughter is a very proper way of commemorating them.
We find all sorts of things funny because humour is not just a way of expressing jollity, it is also a way of dealing with pain and suffering. This is why the trenches of the first world war bred so many jokes. This is why the emancipated inhabitants of countries lately under the yoke of the Soviet empire have stopped laughing so much.
All sorts of things make us laugh. But do you ever laugh at the Cosmos? Why would you do that?
You laugh at the whole situation as it is. The whole situation, as it is, is absurd — no purpose in the future, no beginning in the beginning. The whole situation of Existence is such that if you can see the Whole — such a great infinite vastness moving toward no fixed purpose, no goal — laughter will arise. So much is going on without leading anywhere; nobody is there in the past to create it; nobody is there in the end to finish it. Such is whole Cosmos — moving so beautifully, so systematically, so rationally. If you can see this whole Cosmos, then a laughter is inevitable.
He goes on to tell a very charming story about three Buddhist monks, and the funeral of one of them. Read it here.