As Valentine's Day unfolds, authorities will be keeping a close watch on teenagers out of concern that their expression of love will turn sexual.

"We will check entertainment venues to prevent children from having pre-marital sex," Akradej Sukrachart, an education official in charge of monitoring student behaviour in Khon Kaen, said yesterday.

He said premarital sex could lead to many problems.

His office has already called on schools not to promote Valentine's Day, otherwise students would be too obsessed with the festival.

Police are threatening to impose jail terms and fines on owners of entertainment venues and "love motels" for allowing underage children in.

"Offenders will face up to three months in jail or a maximum fine of 30,000 baht (US$933),or both," said Maj General Wimon Pao-in, head of the Royal Thai Police's Children, Juveniles and Women Division.

Wimon said police patrolmen would also monitor teenage behaviour in public parks across the country.

"We will issue rebukes for any teenager who behaves improperly," he said. "We will have their parents pick them up if they are found roaming after 10pm".

In Nakhon Ratchasima, officials and police officers will inspect apartments, guest houses and mansions to ensure that students are not hanging out for the wrong reasons.

"We have to do this because we want to prevent unwanted pregnancies and drug abuse," said Kriangsak Khunwises, the head of Nakhon Ratchasima's social development and human security office.

A pharmacy owner in the northeastern province said many female students bought morning-after pills, while male students bought specially designed condoms yesterday.

"I am saying this because I want society to know what really happens," the pharmacist said.

In Bangkok, public park officials will also monitor teenagers. "If improper behaviour is detected, we will issue rebukes," deputy Bangkok governor Bannasophit Mekwichai said, adding that all 23 parks in Bangkok will close at 9pm.

In Phichit, public-health officials yesterday handed out condoms after a survey showed that a number of teenagers plan to have sex today.

In response to the authorities' approach to the Season of Love, 13-year-old Dolhathai Themsinsuk urged the authorities not to be too pessimistic.

"I understand they are concerned about us, but please don't be too pessimistic," the young student said.

While Dolhathai acknowledged that many teens would want to have sex on Valentine's Day, she said many others would completely ignore it.

"It depends on their up-bringing," she said. "As Valentine's Day is a day of love and happiness, people can express their love not just to their boyfriend or girlfriend but also their family."

Thanapum Petcharayut-taporn, 18, welcomed the authorities' measures because she felt they would benefit those who behave well. "I think it is good the authorities will beef up their checks in risky areas. If we don't do anything wrong, we don't have to worry."