Locals call them Red Trucks and use them as their main transport since there are no buses in Chiang Mai. There are no seat belts but these vehicles carry up to 11 passengers and are surprisingly comfortable. No need to worry about safety though. The drivers generally keep to a speed limit so they can stop to pick up passengers, sometimes blocking the traffic and causing rage among drivers who are minding their own business. But hey, at least tourists love them when they don't charge too much.
These vehicles are some of the most unique services in Chiang Mai. It is also worth mentioning that tourists can hire one of these trucks for the day and most drivers are willing to take them anywhere in Chiang Mai, even if it means certain death from falling off the roads to the top of Doi Inthanon.