President Kan Trakulhoon said weak domestic consumer confidence and an economic slowdown are also hurting the industry.
Cement demand for the industry dropped 6.5% on year in the first quarter and 8% in the second, he added.
"So far in this quarter, consumption is still recording negative growth (compared with last year)," Kan said.
But demand will likely level off next year, and start growing in 2009 when mega infrastructure projects are being constructed, he said.