Thailand has one of the highest teenage pregnancy rates in Southeast Asia, public health officials say, and faces HIV infection rates among its gays comparable to those in Africa's AIDS hotspots.
The February 14 celebrations are a popular Western import in tourist-friendly Thailand, but the Bangkok Metropolitan Administration is worried about teenagers making love.
Media surveys have shown teenagers in Thailand pick Valentine's Day as the perfect day to lose their virginity.
"If kids really love each other, it's better for them to go and free birds and fish or go to the temple," Pirapong Saicheua, an official of the city authority, told Reuters.
Freeing caged birds is an auspicious Buddhist ritual that believers in Thailand and elsewhere in Asia see as a way of enhancing their merit, or karma.
"Better to put your minds at ease," Pirapong added.
"Don't obsess over something inappropriate for your age."
Predominantly Buddhist Thailand remains mostly conservative despite its reputation as a hotspot for gay bars, nightclubs and massage parlours.
This year, an administration worried over the spike in teenage pregnancies has made available 3.5 million condoms in 68 healthcare centres and 10 city hospitals.
Thailand's health ministry also plans to install condom vending machines in high schools, said Sophon Mekthon, who heads the ministry's disease control department.
Most students welcomed the project, first tested in 2010, but it was opposed by parents who fear the machines could encourage teenagers to have sex.
"Two out of three kids gave positive feedback, but around 90 percent of parents strongly disagreed," said city official Pirapong.
Still, young people in Bangkok say there is little chance of moral guardians persuading them to rein in sexual activity.
"I think sex can't be prohibited," said Khemaphat Santong, a 21-year-old student at the city's Chulalongkorn University.
"I mean, in some public places, yes, but stopping someone from doing it entirely is impossible."
