I would think your ideal tank would be 48x30x30". Anything taller would be a pain to get stuff off the bottom easily. Now if you have shorter arms 30" tall might be a bit of a stretch to reach the bottom but I found it a very nice height.
Now most would want to put the tank on a stand of some type or another, the reason for this is that if you have it sitting on the floor, there is a greater potential for things to roll into or bump your glass panels. There is also the benefit of placing your filtration under the tank so it wouldn't distract to much from the beauty of the scene your trying to create.
One benefit to have the 30" wide tank is that you have so much more room to decorate your tank so you can have multiple zones in your aquarium. Since your in Bangkok, I'm figuring your having that tank made so the biggest consideration would be the height since it would dictate how expensive or much more expensive your tank will cost. Remember that the more volume you can give your fish, the better off they are going to be.
Now most would want to put the tank on a stand of some type or another, the reason for this is that if you have it sitting on the floor, there is a greater potential for things to roll into or bump your glass panels. There is also the benefit of placing your filtration under the tank so it wouldn't distract to much from the beauty of the scene your trying to create.
One benefit to have the 30" wide tank is that you have so much more room to decorate your tank so you can have multiple zones in your aquarium. Since your in Bangkok, I'm figuring your having that tank made so the biggest consideration would be the height since it would dictate how expensive or much more expensive your tank will cost. Remember that the more volume you can give your fish, the better off they are going to be.