I can sing a rainbow.

"Red and yelow and pink and green
Purple and orange and blue..."

There must be more than 14 taxi companies in Bangkok. Just name any color of the rainbow. They have it there. Even the different hues. As you can tell, there're no problems at all getting a cab in Bangkok. Just stand a little near the road, and various taxis/tuk-tuks/motor-taxis will stop for you. What I hate about public transport in Bangkok though, is having to haggle for a decent fare (when you're desperate), or demanding that the driver turn on the meter (though the meter on the green-yellow taxi is almost always rigged).