The Meteorological Department on Sunday reported that as of 4pm tropical storm "Kujira" was centred about 340 kilometres southeast of Da Nang, Vietnam, with maximum sustained winds of about 75km per hour.
The storm is moving slowly in a northerly direction and expected to cover Hainan Island and the southern part of China during June 21-24.
This condition may cause the eastern part of the Northeast of Thailand to have more rain until June 25.
Travellers going to Hainan Island and Hong Kong are advised to check on the weather forecast before their departure.
The department further announced that the southwest monsoon over the Andaman Sea, the South and the Gulf of Thailand is intensifying. Scattered rain and isolated heavy rain will remain over the eastern and western coasts of Thailand as well as the South.
Waves in the upper Andaman Sea and the upper Gulf of Thailand will remain strong. All boats should proceed with caution. Small boats in the upper Andaman Sea should stay ashore during June 21-27.