Thailand's industrial sentiment index declined to 84.7 in May from 85.3 in April, the Federation of Thai Industries said on Wednesday.
Sentiment was weighed down by the continued slowdown in the manufacturing sector, as well as labor shortages, and the risks arising from the war in the Middle East.
The body said some industry groups have yet to benefit from growth in exports and foreign direct investment.
Rising imports of consumer goods, particularly cosmetics, jewelry, and furniture, combined with inflation from higher production costs also weigh on consumer purchasing power and squeeze operator profit margins, the federation said.