The ministry also said it changed its 2019 estimate for exports, a key driver of growth, to a fall of 0.9% instead of a 3.4% rise.

However, the economy will be helped by a $10 billion stimulus package approved by the cabinet on Tuesday, it said.

The outlook downgrade came a day after Thailand reported second-quarter growth of 2.3%, the weakest annual pace in nearly five years.

Southeast Asia's second-largest economy expanded 4.1% last year, the best in six years.