* Noble says on Monday that Jeffrey Frase resigned as co-CEO
* Noble Group shares fall below S$0.20
* Moody's doubts Noble's ability to generate profit, cash flow
SINGAPORE, Nov 14 (Reuters) - Shares in Singapore-listed Noble Group on Tuesday tumbled as much as 12.7 percent to their lowest in nearly two decades, after Jeffrey Frase resigned as co-chief executive officer (CEO).
The beleaguered commodity trader said on Monday that Frase had resigned as co-CEO and head of the firm's oil liquids business, which Noble is in the process of selling to trading house Vitol.
Noble Group Ltd's shares on Tuesday slumped as much as 12.7 percent to S$0.192 ($0.1411), their lowest since May, 1999.
At its peak, Noble was Asia's biggest commodities trading house, with ambitions to rival Europe's leading merchants like Vitol, Glencore or Trafigura.
But shares in the company have collapsed from a high of over S$17 in 2011, wiping billions of dollars off its market capitalization to just S$292 million.
Noble, which has been criticized for its accounting methods, has failed to profit from recovering commodities markets since 2016, selling off core businesses to service debt.
"The company is selling its assets to help reduce debt ... However, it is highly uncertain whether these sales will raise sufficient proceeds to meet its debt maturities and cash outflow over the next 12 months," Moody's said in an investor note on Tuesday.
Fitch, another rating agency, said "we expect Noble's cash flow from operations to remain weak due to a lack of liquidity available to the company."
Noble declined a request for comment from Reuters.
Despite a surge in commodity prices this year, including coal, oil and natural gas <LNG-AS>, Noble piled up a loss of more than $3 billion in the first nine months of 2017, leading to fresh doubts over the company's future.
"The proposed disposals would substantially reduce Noble's scale and global reach, challenging its ability to generate profit and cash flow to service the remaining debt," Moody's added. ($1 = 1.3606 Singapore dollars)
(Reporting by Henning Gloystein; Editing by Joseph Radford)