I reckon its due to their lack of exercise.
Most of the guys on Buakhao with funny walks are not exercising regularly, the body starts to stiffen up.
That and other health problems, overweight, diabetes, etc will affect your ability to walk freely.
The bar girls on Buakhao call out to these guys walking, yelling sexy man but sadly most are dead man walking.
Some people are so strange, I've got mates, clever guys, PhD's, Masters but they self abuse by smoking and eating poorly.