While renting and driving a car in Bangkok borders on suicide,
renting your own transport in Chiang Mai is a great way to get around
if you want to visit places outside the city.
As a general rule,
ten kilometers outside Chiang Mai center, in any direction, and
you'll have a relatively clear passageway.
Ensure that you have a valid driver's license since it's possible you will be stopped at random police roadblocks. An international driver's license is required in Thailand to drive a car although you can usually get by without one. It's a good idea to bring your normal license so you have something to flash for anyone wearing a uniform.
Chiang Mai has both multinational (Hertz,etc) and local car rental firms and they offer a wide variety of vehicles: saloons, 4-wheel drive jeeps, family wagons etc.
About 1000 baht for a basic saloon and rising for the more specialized/luxurious
vehicles. Although gas prices have increased drastically it's still
cheap when compared to Europet.
It is also feasible to rent a privately owned car and driver,
usually the car's owner, for around the 1000 - 1500 baht per
day. That price should include petrol.
Some travelers prefer this since
the
driver usually speaks English and can be extremely helpful, offering
various insights, helping to order food / bargaining etc etc.
There's
something special about mixing with locals when visiting strange
places.