Appearances

What makes Thai people always do a preliminary judgement through the overall appearances?

How come a person who wears tee and jeans not to be working in an important role and position in an organisation?
Also, how come that person not to be receiving an appropriate respect regards the way he or she works?

Looking through myself, I think I may need to change the way I dress. The clothes make my appearances being "a junior planner" to surround(er) eyes.....they don't even know who I am, and how I work.