Tropical cyclone Mala hit five provinces in the North and Central regions yesterday, prompting a warning from authorities.

Residents in 13 provinces have been told they could face heavy rainstorms and landslides from today until early tomorrow.

The five afflicted provinces are Mae Hong Son, Chiang Mai, Tak, Lampang and Uthai Thani. The other eight provinces at risk are Chiang Rai, Lamphun, Sukhothai, Kamphaeng Phet, Nakhon Sawan, Kanchanaburi, Suphan Buri and Ratchaburi.

The weather bureau said the worst hit area was Mae Hong Son, which has suffered storms since Friday evening.

"Heavy rain will easily cause wild and flash-floods in certain risk areas," said Supharerk Tansrirat-anawong, director general of the Department of Meteorology.

The latest monitoring showed that the cyclone continued to grow in strength but it is expected to peak tonight before winds slow down from about 4am today.

Cyclone Mala formed in the Bay of Bengal and crossed the Burmese coast at 4pm yesterday. The storm, with maximum wind speeds of 120kph, was 500km north of Ran-goon and travelling north at 10kph.

"Residents in the 13 potential afflicted provinces should closely monitor the situation through our announcements," the director general said.

Supharerk said the department had warned governors of the 13 provinces to prepare for Mala. Each governor would contact local authorities to prepare to help any villages hit by the cyclone, he said.

Residents affected by the storm could ring the department hotline 1784 to get help 24 hours a day.

At Mae Hong Son, heavy rain began on Friday evening. The local weatherman said 46.9 millimetres had fallen by 10am yesterday.

Official Khomsan Suwan-ampha of Mae Hong Son Provincial Office said he made urgent calls to seven district heads to prepare for possible landslides and flash-floods. Preparations were also being made to remove villagers to higher areas, if necessary, he said.

Chiang Mai Governor Suwat Tantiphat said he had prepared evacuation plans for villages in three districts at risk - Mae Chaem, Om Koi and Hord, which would be monitoring round the clock.

Bunkia Kunatharnkul, the senior official at Mae Chaem district, said he had been closely monitoring the amount of rain that has fallen and would announce evacuations if it reached 100 millimetres. Yang Luang village was vulnerable and had experienced two landslides recently, he said.

Kanchanaburi Governor Cherdwit Ritprasart ordered officials to prepare for the cyclone, especially in the high-risk districts of Sangkhlaburi, Srisawasdi, Thong Pha Phum and Saiyoke.

Fishermen have been told to prepare for two-metre waves in the Gulf of Thailand and the two to three metre waves in the Andaman Sea.