One of the things that sets northern Thai cuisine apart from the rest of the country is the rich tapestry of vegetables used. This is largely a function of availability. The more temperate northern climate is well suited to growing cool weather vegetables such as cabbages during what the Thais call the "cold season", while still allowing the tropical vegetables to be grown the rest of the year.

Vegetables on sale in one of Chiang Mai's markets.

Although some Buddhist schools of thought demand a strict adherence to a vegetarian existence, most Thais are happily omnivorous most of the time. However, each year the descendants of the Teochew Chinese observe a vegetarian festival, usually sometime in October or sometimes late September. The resort island of Phuket in southern Thailand is famous for its extreme version of this festival, but in fact the practice of avoiding meat for about 14 days is observed nationwide, and many non-Chinese Thais take part as well.

During the vegetarian festival, some regular food stalls will convert to vegetarian only, some will sell more vegetarian dishes than normal, and many special stalls will open just for the festival. Thais have become quite adept at making versions of their favorite dishes that adhere to the principles of the vegetarian festival. Hence, you may see prawn tom yum soup made without prawns. In their place will be fake prawns molded from a paste of flour, nuts and perhaps soy bean.

The rules governing this festival are a little more complicated than simply abstaining from consuming meat. Some other foods are prohibited as well, most notably anything related to the onion, including garlic, shallots and spring onions. Strict adherents will even have different cooking utensils for use only during the festival, so that they remain 'untainted' by coming into contact with meat.

The Thai vegetarian festival is related, albeit remotely, to the "hungry ghost" festival observed by many Chinese communities around the world. The belief is that during this time of year, the gates of heaven (and hell) are opened to give our ancestors a chance to come visit us. By observing a strict vegetarian diet, participants in the festival hope to show their ancestors that they are living a virtuous life to honor them.

One of Chiang Mai's main vegetable markets is found at the Wororot Market on the banks of the Ping River. Although the current market structures are only about 30 years old, owing to a fire that burned down the old buildings in the 1960s, there are been a market in this area for hundreds of years. When he visited Chiang Mai in 1886, the British Minister-Resident Sir Ernest Satow recorded this impression of the market:

"By far the most remarkable sight which Chiang Mai affords is the early morning market. To this between two and three thousand women flock in every day from the surrounding country, each bringing her small supply of goods for sale, and coming in some cases from long distances, even as far as from Lamphun itself. Their wares are laid out on mats spread on the ground, behind which they squat in little groups of twos and threes. No shouting or loud-voiced chaffering over sales, as is the case with the Siamese market-women in Bangkok. Many of them wear a bunch of flowers at the back of the head. The stock-in-trade of a group seems to be of not great value; a few half dried chillies, some bundles of cut tobacco, three or four pieces of petticoat cloth, a pile of buffalo-hide wafers sprinkled with sesame seed, or a few pounds of pork would furnish out half a dozen of them. It is seldom that you see either fish or rice exposed for sale, and I have no idea where the people who deal in these principal articles of food are to be found. The only shops in the town are small booths which line the street between the first and second gates, and here you may buy English cotton goods, yarns, and lacquered boxes from Burma. In the cross street outside, which runs northwards and parallel to the river, you can procure a few vegetables and miscellaneous European goods from Chinamen or their native wives."

Things have changed a bit since Satow's time. The variety and abundance of goods is much better, but alas the ladies no longer wear bunches of flowers in their hair. Sir Ernest's visit was little more than a 100 years after the Siamese had helped to force the Burmese out of Chiang Mai and the rest of Lanna. Near the end of their occupation of the city, the Burmese forced most of the city's residents into slave labour around present-day Mandalay, practically turning the city into a ghost town. Many of the city's temples and civic structures had been abandoned for many years during the occupation, and it was only in the twentieth century that the city really began to recover its former glory.