Dense fog is expected to blanket Suvarnabhumi Airport and neighbouring areas again this morning.

Poor visibility may force flights to be diverted to other airports similar to yesterday's (Jan 13) scenario.

Airport general manager Serirat Prasutanond said yesterday flights would be diverted to Don Mueang, U-tapao and Chiang Mai International airports if necessary.

According to Aeronautical Radio of Thailand deputy director Kamthorn Sirikorn, fog forced six flights to be diverted from Suvarnabhumi yesterday morning.

"They were mainly flights from Europe," he said, adding some Thai Airways Inter-national and Nok Air flights from Chiang Mai were also affected.

However, he said it was normal for fog to cause visibility difficulties and for pilots to prefer to land at their alternate sites.

Kamthorn said Suvarnabhumi air-traffic control would liaise with pilots over possible diversions.

"Fuel is a key factor," he added, "If aircraft have sufficient fuel, we put them in a holding pattern. If not, Don Mueang, U-tapao and Chiang Mai airports will be used."

He said the fog was often a problem at Suvarnabhumi because of its open nature.

Fog affected Chiang Mai yesterday, too, affecting flights to and from there, its airport director, Commander Prateep Vijittho, said.

Meteorological Department director-general Suparerk Tansriratanawong warned motorists in Bangkok and nearby provinces to be extra cautious in the morning.

A weak, high-pressure system over the Northeast, the Central plains, including Bangkok, and the east is causing the morning fog. It could continue until tomorrow.

Meanwhile in Chiang Rai, a Thai tourist fell to her death at a scenic cliff at Phu Chi Fa Forest Park yesterday.

Park officials rushed to issue safety warnings to visitors following the accident.

As many as 10 park officials had been deployed at the vantage point to inform tourists of possible dangers.

Ropes went up to prevent tourists from venturing into areas that were deemed dangerous. More warning signs will also be posted.

"Officials will be deployed at the cliff until Valentine's Day (Feb 14)," park chief Banchan Ruamsiri said.

The measures were ordered after Panthita Sakornjan, a 26-year-old Bangkok nurse, plunged to her death shortly before 6am.

She was vacationing with friends at the park.

The accident took place even though four warning signs were posted near the area.

"Fog may have obscured the warning signs," Bancha said.

He explained that the safety signs could not be made bigger because Laos had claimed ownership of the vantage point as well. It would protest whenever a big structure was erected.

It took officials several hours to retrieve Panthita's body from the ravine.

The winter season makes the mountainous area a popular destination for many locals.

In Chiang Mai, more than 5,000 tourists visited Doi Angkhang farming station as its temperature dropped to 3 degrees Celsius.