According to data compiled by Toyota Motor Thailand, accumulated sales reached 792.328 units.
In the first 11 months, Honda suffered the most, with a 53 per cent plunge in sale to only 93,113 units.
Toyota, of which product portfolio includes pick-up trucks, witnessed a 27.3 per cent drop to 293,954 units. Isuzu's sale also dropped by 23.2 per cent, lower than the annualised average.
Yet, the industry seemed to suffer less from weak demand compared to early this year, as November sale dropped by only 21.8 per cent.
In the month, a number of 73,068 units were sold.
In a statement, Vudhigorn Suriyathantananont, senior vice president at Toyota Motor Thailand, did not expect a sharp recovery in December.
"Statistically, December has been the best-selling month. Though in this year, despite the Motor Expo, political stability and clearer public investment plan, consumer confidence edged lower in 2013 due to external factors which delays the full recovery in the export and tourism sectors," he said.
Exacerbating the situation is also low farm product prices, he added.