During the annual ten-day “Tesagin Kin Pak” vegetarian festival, yellow flags representing Buddhism and good moral conduct flutter in the wind above entire neighborhoods, while tiny mobile street carts with a lone yellow flag advertise vegetarian-friendly food.

Glistening tofu, noodles with bean sprouts, desserts made with sesame and ginger and steaming hot vegetable broths abound.

“I give up meat to cleanse the spirit so that my family will prosper,” said Ploy Sudham, who owns an art gallery on the outskirts of Bangkok's Chinatown.

Every year during the ninth Chinese lunar month, the country's Thai-Chinese community - often third or fourth generation Chinese who grew up in Thailand but are brought up with Chinese customs - observes ten days of abstinence.

Eating meat, having sex, drinking alcohol and other habits thought to be vices and pollutants of the body and mind are cut out entirely by the truly devoted, who also wear only white. The belief is that nine gods come down from heaven to inspect the earth and record the good and bad deeds people commit.

The festival began over 150 years ago on the popular tourist island of Phuket, some 840 km (521 miles) south of Bangkok.

Legend goes that a wandering Chinese opera troupe fell ill with malaria while performing on the island but after sticking to a strict vegetarian diet and performing rituals to two Emperor Gods the troupe made a full recovery.

Locals, impressed by what they took to be a miracle, began eating a strict vegan or vegetarian diet once a year.

Its sister festival in Bangkok's Chinatown or “Yaowarat,” one of the earliest Chinese communities in Thailand, is equally deserving of a visit.

The crowded roads and winding alleys are pure chaos with their honking taxis and a handful of aggressive street hawkers.

But during the festival, vegetable mania takes hold and reaches almost comic levels. “Are you sure that's vegetarian?” asked Chanun Marukpitak, 34, a Bangkok office worker who eyes a stall of roast peanuts.

As night falls, neon signs light up. Crowds gather to watch vendors expertly throw chilli, basil and vegetables into oily woks.

Sitting quietly in the corner is Pawika Pengnineht, 75, great-grandmother to a large brood. Four generations of her family have sold food and drinks in Chinatown but that will end with her great-grandchildren, who favor office jobs.

“White symbolizes purity and by giving up animal products, which means killing living beings, we aim to start a clean slate once a year,” Pawika said.

Other practices related to the vegetarian festival can be seen here.