Not all streets and roads in Thailand have sidewalks. Sales stalls, pedestrians, cars, motorcycles, and everyone else shares the space. Therefore, be very attentive to traffic and make sure to walk in the opposite direction of the motorized traffic in two-way streets and on the left-hand side if you are walking in the same direction as traffic in one-way streets. Although Thais do not always adhere to the traffic direction, it can give you fewer surprises.
But even if there is a sidewalk, it does not necessarily mean easy progress. Sales carts with food or other goods often take up part of the space. Furthermore, you will often encounter pipes or other objects sticking out of the ground. Therefore, always keep at least one eye directed downward to avoid getting hurt.
Often, you get the feeling that the sidewalks are not for pedestrians. Instead, they are for things not suited for the road, such as trees, lampposts, bus shelters, and big mailboxes. Of course, the workers place the various objects where it is easiest to put them; that is, not at the edges of the sidewalk but in the middle of the sidewalk.
Be careful at junctions where the sidewalk ends. The curbs are much higher in Thailand than in many other places because they account for heavy rain showers.
Thailand is a land of contrasts, and that goes for the sidewalks as well. Thus, while it can be hard to get around on some sidewalks, it is a pleasure to walk on other sideways. The sidewalks in Bangkok's shopping area are of reasonable standard without too many surprises, and here you will also find practical skywalks. Skywalks are elevated and covered sidewalks above the traffic; thus, you can walk safely, and the overhead cover protects you from the rain and sun.
The skywalk often leads directly to shopping centres and Skytrain stations.
As you can deduct from the above, Thailand is not wheelchair-friendly. However, this does not mean wheelchair users should stay away from Thailand. You can still have a fantastic vacation, even if you are on wheels, but your vacation may require more planning. Brian Jensen has created a website with a lot of good advice and descriptions about being a wheelchair user in Thailand. Read more at his website.