The advisory forecasts strong wind and waves “as the strong southwest monsoon prevails over the Andaman Sea and the Gulf of Thailand” through to Sunday (July 22).
Strong wind waves of two to three metres tall, reaching above three metres thundershowers, are forecast.
Abundant rain with isolated heavy rain are likely in the Central, the East and the South, said the warning.
For Phuket, southwesterly winds are forecast to reach between 20-40km/h.
“All ships should proceed with caution, and small boats in the Andaman Sea keep ashore,” the warning, issued by TMD Director-General Wanchai Sakudomchai, advised.
“The coast of the East and the western South should watch for inshore surges,” the warning added.
The weather advisory comes as tropical storm ‘Son-Tinh’ over the upper South China sea with its maximum sustained wind of 70km/h continues to move westward at a speed of 35kmh.
Son-Tinh is expected to move to the Gulf of Tonkin by this morning (July 18) and move to upper Vietnam this evening.
“It will have an effect on the upper Thailand with more rain and isolated heavy to very heavy rain during July 18-21. People should beware of severe weather conditions and stay tuned for the weather forecast,” the warning urged.