The "Crank That" hitmaker first revealed his big pay day last month on Twitter, but didn't reveal any details.
"USD 400 million deal confirmed. I still they think they low balled me though. I was thinking 2 or 3 billion," he wrote.
Now the 25-year-old has announced the lucrative partnership is with a leading online poker platform.
As part of the five-year deal, the star will promote the company's various properties through his Twitter profiles.
"I invest in things I understand. I enjoy music, and of course gaming. Being an influencer is a form of currency. Having portfolio diversification is critical if you want to be an effective brand ambassador. With regards to World Poker Fund, I believe in its strategy, its team, the vision, and management's ability to target its financial goals," Soulja Boy said.