"The suspension of operations has hurt not only the overall economy but also the Kingdom's image," said Thanit Sorat, vice chairman of the Federation of Thai Industries and chairman of its logistics club.
The sealing off of the country's aviation gateway would cost the air cargo business Bt1 billion per day, as freight handling has had to be temporarily halted, he said.
Without air cargo operations, perishable goods such as fruits and vegetables as well as electronic and auto parts cannot be transported.
Finance Minister Suchart Thadathamrongvech conceded that the government's economic stimulus package may fail to boost growth compared to the damage inflicted by protesters in shutting down Suvarnabhumi.
Economic growth will not reach 5 per cent this year, he said. The negative impact on tourism would be long-lasting because the incident crushed tourist confidence, he said. Risk premiums will rise, imposing a heavy cost on the tourism industry.
As the protesters also blocked a meeting of Parliament, the government could not implement mid-year budget spending, he said. The government plans to increase spending by more Bt100 billion to shore up the economy already weakened by the global financial crisis.
The government could not however cut value-added tax from 7 per cent to 4 per cent, as proposed by some analysts. The current VAT rate is already low, he said.
Customs officials said goods worth Bt12 billion a day pass through customs procedures at the airport, but customs operations have now been paralysed.
Poj Aramwattananont, president of the Thai Frozen Foods Association and major seafood exporter Wales Group Factories, said the political conflict should not have spilled over to the international airport, which would send shock waves through tourism and trading industries, and even the economy as a whole.
"The political conflict is hitting the overall economy, which is unfair to all Thais," he said.
Richard Hames, a professor at the Asian Foresight Institute of Dhurakij Pundit University, said foreigners did not understand why Thais had allowed the situation to happen.
"It's a splinter of glass in the finger. Although it's small, it hurts the country very badly," he said.
It is especially damaging to a tourism country. "I believe that it will take at least three years for the economy to recover."
Dusit Nontanakorn, vice chairman of the Thai Chamber of Commerce, said the repercussions of the civil action were beyond estimate and it was likely to scare away tourists.
He wants to see it end as soon as possible.
Dej Pathanasethpong, president of the Thai Garment Manufacturers Association, said the situation was more serious than previously, as businessmen cannot run their plants as normal.
"What Thailand is losing is not only foreign income from exports and logistics, but also the most important thing - its credibility," he said.
Wichian Mektrakarn, president of leading cellular operator Advanced Info Service, said he hoped the conflict would end quickly before the whole economy suffers.
Pitaya Phanphensophan, CEO of Coca Holdings International, which has three Mango Tree restaurants at Suvarnabhumi, said the company had decided to temporarily close the branches at 9pm on Tuesday, which would mean Bt200,000 per day in lost business.
Tassapon Bijleveld, chief of Thai AirAsia, said it was too soon to estimate the damage to the budget airline. He will keep monitoring the situation closely.