If you ask some Thais to name a dish that Chiang Mai is famous for then there's a good chance you'll hear 'sai ua' more than once. It's a sausage that can vary a bit in spiciness and is made with several local herbs and spices. It's mostly sold grilled on charcoal, though many of the big shops also sell it 'fresh', wholesale style. Many Thais who come for a holiday or business visit to Chiang Mai would bring some Sai Ua and other Northern foods and snacks back home.
You can find Sai Ua at most markets and the odd road-side food stall. It's mostly eaten with some sticky rice and Nam Phrik Noom: A green chili dip made from long green chilies.
I feel compelled to include the most 'famous' place for Sai Ua in Chiang Mai, which is 'Mengrai Sai Ua' right next to the Sheraton Hotel (formerly named Westin Hotel) before you get to the bridge over the Ping river. (Photo 4, 5 and 6) At 22 baht per 100 grams it's also one of the more expensive ones, and frankly I like the vendor at some nameless market way down the Canal Road past the middle Ring Road a lot better. 8-) He's getting pretty famous himself, and sells his Sai Ua now for 20 baht per 100 grams.