I'm a little late to reply, but I found an incredible place to get great plants, including a large range of Orchids. Hua Hng World Farm just beside Khatib Camp is about 20 times the size of any of the Thompson nurseries, half as cheap and has a gazillion times more variety of plants, pots, fertilisers, potting medium, pesticides...etc. They also have an online store that will deliver to your doorstep.