The last train departs the airport at midnight; so you may or may not make that last train depending on many factors.

What sort of supplies are you looking for - not trying to be noisy but there may be better alternatives?

Very generally speaking there are specific areas which have evolved around the city, which concentrate on having dozens of suppliers for different things, and they are concentrated in one place by product type. So for water supply/filtration systems there are a gazillion shops in Rangsit, and everyone knows to go there.

And there are gardening supply stores simply everywhere. And there are also mobile gardening supply trucks.