Can I only eat it in Chiang Mai?
No. It is a signature dish eaten in many cities of the North. If Chiang Mai is your first taste of Northern food, a bowl of khao soi is a good place to start.
Khao Soi · ข้าวซอย
If you are choosing a meal in Chiang Mai, try khao soi. Egg noodles sit in a coconut curry broth, topped with crispy fried noodles, in this signature dish of the North. Part of the fun is eating soft noodles and crispy noodles by turns. If a lime wedge comes on the side, taste the broth first and then squeeze in a little.

A rich curry broth and two kinds of noodle texture define it. The noodles on top start out crispy and slowly soften as they touch the broth. Taste the broth before and after you add the condiments and you can enjoy different flavors in a single bowl.
Try the crispy noodles on top first, before they get soaked in the broth.
Khao soi is a well-known dish on a trip to Chiang Mai, but it is also eaten in other cities of the North. Unlike a Northern meal of sticky rice and side dishes, it puts noodles and broth in one bowl. It is a good pick when you are eating alone or want a simple lunch.
No. It is a signature dish eaten in many cities of the North. If Chiang Mai is your first taste of Northern food, a bowl of khao soi is a good place to start.
There are several menu items, such as chicken or beef. Look at the main ingredient listed on the menu and choose the one you want. Not every restaurant uses the same meat.
If you want to read more about the food and the regions behind it, these sources are a good place to start. Ingredients and recipes can vary from one restaurant to the next.
Sharing image credit: Takeaway · CC BY-SA 3.0