I think in the mid-70s "The Book of Lists" took a shot at this one, based on a lot of traveler reports. A coastal city in Colombia came out as #1, followed by Kotzebue, Alaska, followed by Doha, Qatar.

From personal experience I can't say too much for Kalibo, Philippines, Polonnawura, Sri Lanka or, sectionally, the Pettah part of Colombo, Sri Lanka. Though in a way the Chinatown section of Bangkok has a leg up because, while possibly interesting, the sidewalks are still horribly crowded and the vehicular traffic is so thick that the fumes suffocate the place. It really is a health hazard to be outside in that area for any length of time.