BANGKOK (Reuters) - Alarmed by polls showing one in four Thai teens will celebrate St. Valentine’s Day by having sex, police plan to swoop on motels, malls and parks to ensure youths behave themselves on the “Day of Love.”

A couple walk in the sea and enjoy the sunset on Patong beach, in the Thai resort island of Phuket, March 24, 2005. Alarmed by polls showing one in four Thai teens will celebrate St. Valentine's Day by having sex, police plan to swoop on motels, malls and parks to ensure youths behave themselves on the "Day of Love." REUTERS/Sukree Sukplang

The annual campaign to ensure good behavior on February 14 will see city officials turn on all lights at public parks in the capital Bangkok, while parents are urged to make sure their teenagers come home early.

Police and “student inspectors” from the Education Ministry will be checking discrete “curtain” motels to make sure youths under the legal age of 18 are not using them for amorous interludes.

“We will send patrols to check out public parks, restaurants and shopping malls, which are the starting points for potential sexual activities that will be done at home or motels,” Bangkok police spokesman Suporn Pansuea said.

Thailand’s moral guardians are taking action after an Assumption University poll showed 27 percent of 2,400 Bangkok teenagers surveyed said they might have sex on Wednesday.

Despite Bangkok’s reputation as one of the world’s sex industry centers, predominately Buddhist Thailand is generally a conservative country.

This year’s St Valentine’s Day celebrations have been tempered by a sluggish economy after two years of political strife and a 2006 coup, and nationwide mourning for King Bhumibol Adulyadej’s sister who died in January.

Rose vendors have complained about sagging sales because people have less disposable income.

“I don’t think we’ll have robust sales this Valentine’s Day,” Den Yarum, a florist at Bangkok’s main flower market, told the Thai-language Daily News.

A number of annual high-profile events, such as weddings conducted on mountain cliffs, underwater or in hot-air balloons, have been cancelled or postponed due to the 100-day mourning period for Princess Galyani Vadhana.

Bangkok’s “District of Love,” a city office where superstitious couples flock to register their marriages on Valentine’s Day, will be open for business, but the ceremonies will be low key.

“People are still mourning Princess Galyani Vadhana so the activities will be simple, with an emphasis on her love for the people,” district chief Pravit Panviroj said.