You will find local vendors selling standard fruit tree, but you will need someone who speaks Thai as most of them will not properly talk English or if they do a lot of confusion will arise. However most of the 'local' nurseries lack the notion of sanitation so most of the plants have lots of diseases and pests. Thailand doesn't have the clean "peat" we can find in stores in Europe or US. I found that the most destructive in Thai nurseries are nematodes. Almost all the plants I tested had some sort of them.