Jack Ma, China's richest man, was happier earning $12 a month than he is as a billionaire

Jack Ma, the founder and executive chairman of Alibaba, became the richest man in China after Alibaba IPO'd for a record $25 billion last September.

But Ma was just as happy - perhaps even happier - when he was barely making any money right out of college.

After graduating in 1988, Ma worked as an English teacher at a local university in his hometown of Hangzhou, China. He only made $12 a month, according to the documentary about his life called "Crocodile in the Yangtze."

When speaking at a luncheon with the Economics Club of New York on Tuesday, Ma referred to this period as the "best life I had."

When you don't have much money, you know how to spend it, Ma explained. But once you become a billionaire, you have a lot of responsibility.

"If you have less than $1 million, you know how to spend the money," he said during Tuesday's speech. " [At] $1 billion, that's not your money...The money I have today is a responsibility. It's the trust of people on me."

Ma says he feels a need to spend his money "on behalf of the society."

"I spend it our way," he said. "It's a trust."

This isn't the first time Ma has spoken about the burden of being a billionaire. When speaking at a panel at the Clinton Global Initiative in New York, he referred to his days as an English teacher as "fantastic," according to CNN Money. He said anyone with $1 million is "lucky," but when you reach $10 million, "you've got troubles."

After Alibaba's IPO, he told CNBC that the pressure that comes with the responsibility gets to him, especially now that the world is focusing on Alibaba's stock price.

"IPO is great because ... I'm happy with the results," he said to CNBC. "But honestly, I think when people think too highly of you, you have the responsibility to calm down and be yourself."