The planned shutdown of Bangkok by protesters from Jan 13, coupled with the baht's retreat against the US dollar, has already weakened demand for import goods and luxury products in particular, said caretaker Deputy Finance Minister Benja Louischaroen.
Her comments came after both the Excise Department and the Customs Department reported that tax revenue collection for the first three months of fiscal 2014 fell short of goals.
The protest led by former Democrat MP Suthep Thaugsuban began last October to oppose the blanket amnesty bill and now extends to removing Yingluck Shinawatra's government and paving the way to reform.
For the first three months through December, the Customs Department and the Excise Department missed their targets by 6 billion baht and 4 billion baht respectively.
In the October-December period, Customs collected 27 billion baht while Excise garnered 103 billion baht.
The Revenue Department's collection of 356 billion baht, however, exceeded its target by 7.1 billion baht.
Rakop Srisupaat, director-general of the Customs Department, said import value for the first three months of fiscal 2014 fell by 100 billion baht as imports shrank 5% from a year earlier.
The Fiscal Policy Office recently forecast that import value would rise 14% year-on-year for the October-December period.
The Customs Department then estimated that revenue collection would miss its target by no more than 10% for fiscal 2014 if the political impasse improved.
The department aims for revenue collection of 131 billion baht in fiscal 2014.
Somchai Pulsawas, director-general of the Excise Department, said it remains to be seen whether the impact on revenue collection will extend into the second quarter of the fiscal year.
The department aims for revenue collection of 463 billion baht in fiscal 2014, factoring in a planned excise tax hike on diesel to 1.40 baht a litre from 0.005 baht now.
Mr Somchai said revenue collection could fall 50 billion baht short of target if the tax is not raised.
In related news, the caretaker government said yesterday that prolonged protests would damage the country's economy, forecasting economic growth in a range of just 3% to 3.5% in 2014 after an earlier projection of 4% to 5%.
If water management and other infrastructure projects are stalled, growth will suffer, caretaker Deputy Prime Minister Niwatthamrong Bunsongphaisan said after meeting officials of the Bank of Thailand and the National Economic and Social Development Board (NESDB).
"Everything is now disrupted, including the free trade area agreement and attempts at fiscal budget disbursement," he said.
According to Mr Niwatthamrong, in the first three months of fiscal 2014 the state could disburse only 830 billion baht, compared with a target of 1 trillion baht.
NESDB secretary-general Arkhom Termpittayapaisith said the mass rallies will inevitably hit tourism and other sectors, but the state planning unit has yet to evaluate such an impact.
The NESDB said tourism last year was in good shape, with foreign tourist arrivals hitting 26.7 million, exceeding the target by 26%.