Waves in the Andaman Sea and the upper Gulf of Thailand are expected to be 1-2 metres high and over two metres in thundershower areas. All ships should proceed with caution, the department said.
The weather forecast for the next 24 hours:
Bangkok and surrounding areas: Thundershowers in 40 per cent of the areas; temperature lows of 25-27 degrees Celsius, highs of 33-36°C.
North: Thundershowers in 30 per cent of the areas; temperature lows of 23-26°C, highs of 33-36°C.
Northeast: Thundershowers in 20 per cent of the areas; temperature lows of 24-27°C, highs of 35-37°C.
Central: Thundershowers in 40 per cent of the areas; temperature lows of 24-26°C, highs of 35-37°C.
East: Thundershowers in 60 per cent of the areas with isolated heavy rains; temperature lows of 25-26°C, highs of 29-35°C; waves 1-2 metres high and two metres during thundershowers.
South (east coast): Thundershowers in 60 per cent of the areas; temperature lows of 22-25°C, highs of 33-35°C; waves a metre high and 1-2 metres during thundershowers.
South (west coast): Thundershowers in 70 per cent of the areas with isolated heavy rains; temperature lows of 21-25°C, highs of 30-34°C; waves 1-2 metres high and over two metres during thundershowers.