Elon Musk has lost about $31bn, taking him down to second place on the list, according to the index.
The stock market fortunes of Amazon and Tesla, who count their founders as their biggest shareholders, are in close relation to the billionaires’ wealth gains and losses.
Amazon’s share price has surged by more than 18 percent this year, while Tesla’s has dropped by 24 percent.
Despite selling $8.5bn worth of Amazon shares earlier this month, Bezos remains the biggest shareholder in the e-commerce giant with a 9.56 percent stake. Elon Musk has an equity of about 20 percent in Tesla.
In January, a United States judge struck down a Tesla pay package for Musk valued at up to $55.8bn after finding that the process for approving his remuneration was deeply flawed.
Musk, who also runs X and SpaceX, along with Tesla, rose to the top of the rich list in May after toppling Bernard Arnault, the chairman and CEO of luxury goods company LVMH, who now ranks third with $197bn.
Bezos, Musk and Arnault have jockeyed for the top spot in recent years in the ranking, which is based on fluctuations in the stock market and other economic data.