Thai Industries Sentiment Index (TISI) dropped in August on heavy rains and flooding, the Federation of Thai Industries said on Wednesday.
FTI chairman Supant Mongkolsuthree said the TISI monthly survey for August put the index at 92. 5, down from 93.2 in July.
"We witnessed the rainy season last month and that was the main factor putting pressure on purchasing power in the provinces. There was flooding in the northern and northeastern regions," he said.
"The impact was on sentitive products and construction materials."
The FTI maintained its forecast the index will reach 105.6 over the next three months.
The index surveyed 45 industry sectors with 1,045 members. An index above 100 reflects their confidence and a figure under 100 indicates their pessimism about the economy.