If you're planning to ride a bicycle in Bangkok, do so with care. Cycling in such a large metropolitan city can be more risky and challenging than adventurous, considering air pollution and the city's notorious and at times chaotic traffic. Indeed, cycling can possibly even jeopardise your life.
However, if cycling is your thing, there are some perfectly safe and enjoyable rides in and around the city. The golden rule is to be alert and careful at all times, whilst ensuring you are wearing a safety helmet and that your bicycle is in a perfectly roadworthy condition.
In terms of cycling, there are both good and bad cyclists in every country. For Bangkok itself, the bad ones are those with locally-made bicycles. Their brakes and reflectors don't work, and they have no lights. Even though they have gears, these cannot be shifted, their chains are likely to be rusty, saddles are too low, they ride O-legged, and often carry a passenger on the back.
In contrast, the good cyclists ride excellent frames with quality components. Their bikes lack mudguards and stands, are often the latest model and in good condition. They are as fast as the slower motorcycles and indeed do go on roads, where they expect to be respected by their traffic partners. Well, if you consider yourself a good cyclist, read on.
Fortunately, Bangkok traffic police give a cyclist very little trouble since they think cyclists can really make a difference: reduce air pollution, noise and traffic jams. However, if you insist on using their roads, fellow drivers will not hit you for sure, but expect that they will use their vehicles' horns freely, stare at you (at night with the high beam), force you to yield, go dangerously close, cut across your way, shout at you - or even throw things at you! If an accident happens and the driver cares to stop, he will jump up and say; "Why do you ride your bicycle on the road? You know how dangerous this is!"