After suffering billions of dollars of losses on its investment in WeWork, SoftBank Group Corp.’s Vision Fund is scaling back its high-risk investing strategy and focusing more on improving corporate governance at portfolio companies, according to current and former executives at the fund.

Masayoshi Son, SoftBank’s chairman and CEO who also runs the Vision Fund, has told staffers at the fund to push the companies in which it owns stakes to generate cash, these people said, a drastic shift from his earlier demands that they...