Stock investor confidence for the three months through November dipped into neutral territory from bullish in the previous survey, dampened by worries about trade tensions, the country's sluggish economy and listed companies' profitability.
The Investor Confidence Index (ICI) tumbled 21.7% to 102.74 from August's 131.21, according to the monthly survey by the Federation of Thai Capital Market Organizations (Fetco).
An index below 80 points is considered bearish, 80-120 is neutral and over 120 is bullish.
Indices gauging confidence across different groups of investors showed a decline, with the exception of the foreign investor index, which rose marginally and stayed in bullish territory.
Retail investors turned bearish, brokerage firms' confidence declined into neutral, while local institutional investors' confidence edged lower but remained in neutral.
Commerce, energy and utilities, and information and communication technology are the most attractive sectors for investment, while petrochemicals and chemicals, banking and electronic components are the least attractive.
Investor confidence for August to October edged up into bullish territory for the first time in five months amid offshore fund inflows and US monetary policy easing.
The US Federal Reserve's monetary policy manoeuvres had the biggest impact on investor confidence for the three months through November, followed by the Thai government's economic policy and domestic economy, said Paiboon Nalinthrangkurn, chairman of Fetco.
A consensus of analysts also lowered SET-listed companies' earnings growth this year from 7% to 2%, with economic growth dipping below 3%, he said.
The Fed's rate cut is the key factor bolstering investor confidence.
Further monetary policy easing is expected this year and next, said Mr Paiboon.
The SET index had a roller-coaster ride in August, rising to the month's high of 1,700 points early last month, then sliding to the month's trough of 1,590 in the middle of the month. The bourse recovered to trade at 1,640-1,650 points later in the month.
Sombat Narawutthichai, secretary-general of the Investment Analyst Association, said the SET is forecast to move within 1,650-1,750 points during the remainder of the year.
Other positive factors are the government's economic policies and stimuli, he said.
External factors that warrant close attention are the monetary policies of the Fed and European Central Bank, trade negotiations between the US and China, and Brexit, said Mr Sombat. The deadline for Brexit is Oct 31.
