The one interesting impression when I first got to Bangkok was pink taxis.  Its not just one or two, but a whole fleet of Toyota Corolla/Altis painted in bright pink.  They have a few Taxi companies, and pink was my favourite.  The second thing that left my an impression on my first day in Bangkok was the Bus Kilang.  In Malaysia (in Penang at lease), the bus kilang (factory bus) are mostly painted Blue, dull blue.  The Bus Kilang in Bangkok, has airbrush cartoons on them.  I tell you, they come in so many variations, every bus is a masterpiece.  The next time you drop into Bangkok, dont forget to take a pink taxi and look out for air brush factory busses.