The cyclone, which was hovering over the central Bay of Bengal as of 4am Friday, was moving north at about 10 km/hr with sustained winds of about 105 km/hr. It is expected to make landfall over Myanmar on either Sunday or Monday (May 14-15).
The TMD advised people in affected areas to beware of the severe conditions that may cause flash floods and overflows.
The department also forecast that from Saturday to Monday, waves in the upper Andaman Sea will rise to 2-3 metres in height and over 3 metres off shore due to strong southwesterly winds. All ships should proceed with caution and small boats in the upper Andaman Sea should stay ashore until Monday.
Earlier on Tuesday, the TMD dismissed rumours doing the rounds on social media that the country will be hit by two cyclones on Sunday May 14, the day of the general election.
The department has not detected any storms that will hit Thailand from Tuesday to next Monday and no storms are forming over the South China Sea, Digital Economy and Society Minister Chaiwut Thanakamanusorn told the press on Tuesday.
He added that although Cyclone Mocha will not make landfall in Thailand, its influence will unleash heavy rain in the North from Thursday to Sunday.
The southwest winds will strengthen on Sunday, he added, bringing heavy rain to about 60% of the country.