BANGKOK: Thailand's domestic vehicles sales in May fell 26.2 percent, capping 12 months of decline, the industry said Saturday.

A total of 40,539 units were sold in the kingdom, with commercial vehicle sales worst hit, falling by nearly a third.

Passenger car sales fell 18.3 percent, representing the worst monthly decline this year.

The industry hopes for better data from June's sales but is concerned that rising oil prices could dent any improvement, according to Toyota Motor Thailand, which compiles industry-wide data.

"Based on our statistics, June sales are always the highest for the second quarter and production has been boosted to clear a backlog of orders," the company said in a statement.

"But as oil prices keep rising it could affect our car market," it said.

Combined sales from the three largest Japanese auto makers -- Toyota, Isuzu, and Honda -- continued to dominate Thai auto market, accounting for 79.4 percent or 32,214 units of sales.