Dara Thai is a great restaurant located near the train tracks on the main street in Flagstaff. The restaurant is really bustling on the weekends and is an obvious choice for locals who want Thai food.
The service is satisfactory and the food is good - I wouldn't say it's the best Thai food I've ever eaten, but it will do in a pinch. The food is reasonably priced and for the quantity you receive, I'd say the price was very reasonable.
I've been to this restaurant several times - with dates and with groups of friends. It's always a good choice. Just be sure to tell your server the amount of heat you can handle - they can make your dish as hot or as mild as you desire.