Supporters of the People's Alliance for Democracy threatened on Sunday to stage strikes that threaten electricity and water supplies in Bangkok, and to close more airports in the South.
In Bangkok, the union spokesmen of the Electricity Generating Authority of Thailand and the Metropolitan Water Works Authority said workers would take a one-day sick leave on Monday.
Official Thai News Agency said the spokesmen threatened to cut water supplies and electricity to all police stations nationwide.
Media reports quoted PAD supporters in the South as saying protesters could shut down seven airports. The claim appeared credible; the group easily shut three airports last Friday.
PAD coordinator Sunthorn Rakrong told reporters in the South that he had the power to close seven airports: Hat Yai, Phuket, Surat Thani, Krabi, Samui, Nakhon Sri Thammarat and Trang.
In addition, if they wished, anti-government groups could block all roads leading to the South, as far north as Bor Nok in Prachuab Khiri Khan province.
Mr Sunthorn said he expected there would be large protests if Prime Minster Samak Sundaravey tried to enter the South.
Railway service has been halted nationwide. TNA finally reported that all railway service has been halted in the North, even around the key city of Chiang Mai. Assistant stationmaster Silrat Deewajee said he had no idea when service might resume.
The Transport Ministry warned the State Railway of Thailand union on Sunday it might hire outside workers to get the trains running against unless workers ended the sick-out they began last Thursday in sympathy for PAD protests in Bangkok.