Tour operators in Phuket have been told not to take tourists out to Phi Phi, Racha and other islands unless their boats are at least 10 metres long, because of rough seas and high winds in the area.
Puripat Thirakulpisut, director of the marine office of Phuket, said the waves at sea off Karon and other popular beaches on the west of Phuket were two metres high and sometimes more.
A letter had been sent to all tour operators warning them not to take people to Phi Phi, Racha and other islands at this time unless their boats are at least 10 metres long.
The Tambon Karon Municipality had put up red flags along the beaches warning tourists not to go swimming.
Sanyathawat Riewluang, chief of the Phuket disaster prevention and mitigation office, said all local administrations had been told to be alert for possible landslides and flash floods and to have rescue units and equipment ready to help people in distress.
Meanwhile, tropical depression Vamco has brought heavy rain and storms to the eastern part of Thailand.
Rain fell overnight in much of the lower Northeast and continued through the day.
In Trat province run-off from the Khlong Phlu waterfall in tambon Ko Chang inundated many roads and villages, with floodwater 30-80 centimetres deep. A bridge across Khlong Phlu was cut off at one end, closing it to all traffic.
There have also been intermittent power blackouts on the popular tourist island.