Winds of up to 35-40 kmh - with stronger gusts likely - are forecast to make conditions dangerous at sea for small boats.
Snorkelling and dive vessels are advised to stay at anchor on Phuket, the forecasters suggest.
Decisions on whether small boats should put to sea in conditions that could become dangerous are still a matter for the captains of individual vessels.
At last week's honorary consuls' meeting in Phuket City with Phuket Governor Tri Augkaradacha and other administrators, Australian honorary consul Larry Cunningham had the following to say:
''With the number of boats going to Phi Phi in the raining season, we recently had a boat sink with Australians [and about 40 others] on board.
''One Australian family, the husband ended up in the water, in the middle of the ocean, with his two-yeasr-old daughter next to him.
''The wife was also in the middle of the ocean with her eight-year-old daughter. The eight-year-old kept slipping out out of the life-jacket underwater, the mother had to pull her up by the hair several times, because the life-jacket had no buckles and they eventually had to tie knots in the life-jacket to keep the eight-year-old floating.
''When i met them as they came back from Phi Phi the two-year-old appeared very traumatised. I think she will probably have a fear of water for the rest of her life.
''The fact that these boats go to sea in those conditions makes people think that all they [the captains] are interested in is the money.
''They are risking people's lives. They [the captains] were very very lucky that noone drowned in that situation.
''Now we all know the seas are very bad at this time of year. Is there anything the Marine Department can to to reduce this situation from occurring again?''
Phuripat Theerakulpisut, Chief of Phuket's Marine Office 5, said he would look into the matter and make sure all boats had good equipment.