Singh also accused Ward of benefiting from his personal dealings with the company.
SandRidge did not respond to a request for comment by Monday afternoon.
TPG-Axon, which owns 6.7 percent of SandRidge's stock, is pushing to revamp the company's leadership to maximize its value.
Singh said the 5 percent drop in SandRidge's stock last week after the announcement of the company's $2.3 billion sale of much of its Permian Basin holdings is proof the market has lost faith in SandRidge's executives.
“We believe it is because investors fear that any cash the company receives will be taken or squandered by Mr. Ward,” he wrote Monday in a letter to SandRidge's board.
TPG-Axon needs support from more than 51 percent of its fellow shareholders to enact the desired changes at the company.
Another institutional investor, equity firm Mount Kellett Capital Management LP, has urged SandRidge to replace Ward. It contends the company's stock is vastly undervalued.
SandRidge was down 1 cent in trading Monday, closing at $6.25.
Mount Kellett, which owns about 4.5 percent of the company's stock, has said SandRidge should be worth $20 a share.