You'd likely find interesting and unusual orchids on sale at many places, at the market, pasar malam (night markets), pop-up stores and even supermarkets. Not only limited to just dendrobiums and vandas, nowadays different hybrids of oncidiums are more widely seen.
One of the popular ones are the Oncidium Sharry Baby hybrids. They come in several different shades, with the 'Tricolour' variety most common in Singapore. This post on Miss Orchid Girl's blog has more info about them.
Many of the Oncidiums on the market originate from the Taiwanese growers, and are usually grown in a sphagnum moss. While suitable for their climate and growing conditions with controlled watering, these plants inevitably suffer after they are imported here, due to mishandling at the garden centers and overwatering. Coupled with the high humidity of our climate, the moss doesn't dry out fast enough and root rot usually happens.
Be warned, even with extensive root rotting, the plants can still be blooming and appear healthy. It's only after being brought back that the pseudobulbs start turning yellow or mushy and leaves drop, about 2-3 weeks or so. The plant is usually beyond saving by this point.
To avoid this problem, here's what you can do. Always check the roots of the plant before buying, and avoid those that have any signs of squishy, brown or black roots. Healthy roots are white with green growing tips, although the velamen of older roots may be stained yellow or brown depending on the growing media.
After bringing the plant home, it's always a good idea to change the media especially if it is growing in sphagnum moss, bark or coconut husk chips. These types of media are organic and eventually break down and foster conditions that lead to root rot. If the plant is grown in inorganic media like charcoal, then changing the growing media is usually unnecessary.
The pictures below show a plant that has quite a healthy root system. It's been grown in a bark and moss mix which has started to disintegrate.
Remove the old media by giving it a quick soak in water for about 5 minutes, and taking out the bark chips and moss with a pair of tweezers. Avoid any damage to the roots, although the plant should be able to recover from a few broken roots if the rest of them are healthy.
After all the debris is removed, give the roots another rinse in water, and the plant is ready to be repotted in fresh media like charcoal or leca.