A survey of CEOs of 162 listed companies, conducted by the Stock Exchange of Thailand, showed that Samak had become a key risk factor for the economy.
On Tuesday, he was disqualified as prime minister by the Constitution Court for conflict of interest.
If voted back as premier, he would deflate investor sentiment in the capital market where the value of listed firms has already plummeted by Bt1.5 trillion since May.
Kobsak Pootrakool, executive director of the SET Research Institute, said yesterday that more than 60 per cent of CEOs, from companies in eight sectors representing 63 per cent of market capitalisation, put political uncertainties on top of their list of risk factors.
Other risks include the rising cost of raw materials and high oil prices.
"They perceived the government's credibility has weakened since the anti-government demonstration resumed in May. Over 50 per cent of the CEOs are displeased with the economic measures," he said.
"They view the state of emergency has eroded foreign investor confidence, as seen in the plunge of the SET Index from 875 points to 650 points and the loss of market capitalisation.
"If there's a new prime minister with new ministers, the CEOs believe it would ease political tension and pave the way for solutions. The impact on the economy would be limited then."
The CEOs also said that if Samak stages a comeback, the political chaos would drag on and threaten the economy and the new Samak-led administration would be short-lived, lasting no more than three months.
The Thai Chamber of Commerce also voiced opposition yesterday to Samak returning as premier.
Vice chairman Dusit Nontanakorn said the private sector wants a new leader imbued with a high ethical standards, with a clear understanding of conflicts of interest while in office.
The political turmoil could soon turn the country into a broken ship if the new premier is not properly qualified, he said.
The new leader also needs to be a leader for all Thais, not just selected segments of the population.
Charoen Wangananont, president of the Thai Travel Agents Association, said the previous Samak-led government could not resolve the conflict, so should show their spirit by resigning.