Nearly 70 percent of the business operators surveyed between April and November last year said macroeconomic instability had dampened the investment climate, compared to just under 40 percent in 2004.
More than 60 percent said uncertainty over government policies had weakened the investment climate in 2007, against 30 percent in 2004, the survey said.
"Business operators' perception on the investment climate in Thailand significantly dropped in 2007," Xubeu Luo, a World Bank economist, told reporters.
In addition to the political turmoil, a shortage of skilled labour, poor access to capital, inadequate but costly regulations and unreliable infrastructure also hurt investors' opinions of Thailand, she said.
The findings also showed rising oil and raw material costs had dampened investment in the past year.
The survey involved interviews with more than 1,000 businesses nationwide in nine sectors including autoparts, textiles, electrical appliance and food processing.