Eighteen provinces in the North, East and South should brace for heavy to very heavy rain during this period, according to a Meteorological Department announcement issued at 11am Sunday.
According to the announcement, the monsoon trough is now lying across Myanmar, Thailand's upper North and Laos in conjunction with a low pressure cell in upper Vietnam.
At the same time, the strong southwest monsoon has prevailed across the Andaman Sea, the South and the Gulf of Thailand.
Therefore, more rain is likely over Thailand, particularly Mae Hong Son, Chiang Mai, Chiang Mai, Phayao, Nan, Phrae, Lamphun, Lampang, Tak, Uttaradit and Phetchabun in the North; Chanthaburi and Trat in the East; and, Ranong, Phangnga, Phuket, Krabi and Trang in the South.
Strong wind waves in the AndamanSea and upper part of the Gulf of Thailand are likely to be two to three metres high. All vessels should proceed with caution, while small boats should stay ashore until Aug 18.