And health costs for the four northern provinces were likely to be about the same, officials said yesterday.

With smoggy conditions persisting, prospects for Mae Hong Son remain grim. Readings of dust particles smaller than 10 micrograms in the province stood at 196 micrograms per cubic metre (mpcm). The acceptable level is 120 mpcm.

"The number of flights to Mae Hong Son has reduced from three to just one or two a day," Wisoot Buachum, who heads a co-ordination centre for the Tourism Authority in Mae Hong Son, said.

Wisoot said tour companies had tried to keep their business afloat by arranging vans to transport tourists.

Deputy Prime Minister Paiboon Wattanasiritham said the government would need to hold discussions with Laos and Burma at a more formal level to tackle the smog problem in Mae Hong Son. Smoke from neighbouring countries was the main reason the border province remained hazy, he said.

"We assigned military officers to talk to Burmese authorities, and administrative officials to talk to Laos," he said.

Paiboon said that from March 1 to 23 state hospitals in Chiang Rai, Chiang Mai, Lampang and Mae Hong Son treated 42,026 people for haze-related illnesses such as respiratory problems, skin and eye irritations.

"We estimate that state hospitals, excluding other health clinics, in these four provinces will shoulder Bt25 million in medical costs for treating people affected by the haze this month," he said.