please take a look at my pics in the Fav Pics folder here and let me know what you think
http://www.flickr.com/photos/garylawrence/
Looking over all of your images, frankly the people ones are the worst lit and posed. Most of them need at least some fill flash, almost all of them are center frame and a few have the people looking off to the short side of the frame instead of into it. With the few that do use flash, it seems to be centered over the camera without any power adjustment at all, setting up hot spots. Your landscape shots are much better, but there's really not much money in landscapes or stock these days.
A few examples of images that need improvement:
The lighting is all on the bouquet, but it's harsh enough to wash out the flowers due to overexposure, but there's absolutely no lighting on the face of the couple- a wedding is about the couple, not the flowers, so they either should have been turned to face the light, or better-yet they should have been turned so the sun was a back/rim light and the shutter should have been dragged with an off-axis flash as fill to light up their faces.
The exposure on the background is perfect, the exposure on the couple is under-exposed, and once again their faces should have been lit from flash.
She should be to the right of the frame "looking into it," not in the center. The flash would look better if you were dragging the shutter, and we wouldn't have those distracting background reflections.
Needs less flash power and subject more to the left of center.
The train in Japan and bridge picture would both make great stock images, as would the China and Ayuttaty images, but unless you can get good corporate clients (and with the advent of microstock that's a dying theme) I can't see how you'd make a living that way.
Overall though, the ability to shoot professionally relies significantly more on marketing than technical or artistic skills.
To upgrade the Muy Thai shots, you're either going to have to strobe the venue or get a camera that has better high-ISO qualities, which is a major investment either way, so you have to figure out if it's worth it in terms of opportunities, or if you can get income with other stuff first.
Paul