Man on the train

There were a man and a woman riding in a train compartment.

At one moment in time, the man suddenly started to laugh.

“Are you laughing at me?” the woman asks.
“No” he answered.

After some time the man started to suddenly laugh again.

“Are you laughing at me?” she asks, this time upset.
“No” he answered.

After some more time, the man started to laugh out loud, louder than before.

“Sir, are you laughing at me?” the woman’s angry voice cut his laugh short.
“No, ma’am. I was only telling jokes inside my mind and right now I told one that I didn’t know”.