Certainly depends upon the number of trees you need to have inspected and of course how busy they are. You might be able to obtain info on when the best day/times it would be to show up. I don't believe they take all that long to do the actual inspection. You can bare root prior to getting there, or do the bare rooting at the station. Might bring a bucket so you can fill with water and store your trees in that while working on the next ones. They also offered some sphagnum moss to pack around the roots, but maybe not something to count on unless you check ahead. Have your plastic bags and ties to bag the roots. You will also need your luggage, boxes, whatever method you will be bringing the trees into the country. They will put a seal on that item so that your customs knows that it left their station in the manner that it was supposed to. I would have a late evening flight so that the trees spend as little time bare rooted as possible. Double and triple check your country's regulations and especially if they have any particular methods on soilless products you can use to keep the roots moist.
I think I did some maprang varieties and tried this with around six trees. It was terribly stressful and bare rooting is more time consuming than one would think...if you are being careful. After doing all of this as well as some bare rooting while in PR, I no longer complained about the extra charges for bare rooting when I ordered a tree...especially if shipment required a trip to an inspection station like when coming from Hawaii. It's a pain in the ass!
98% of the places that sell trees in the Bangkok area will all pretty much sell the same varieties of trees. These will be the normal varieties and you will not find anything out of the ordinary. Durian varieties will of course be Monthong, Chanee, Puanmanee, Ganyao. You may find Musang King. There are of course a few online nurseries that sells many more varieties of durian and there is one very close to Bangkok that sells over 50 older varieties. Bottom line...have a good plan and good preparation for obtaining your trees and readying them for transport.