Cyberpunk requires a very large supply chain - you need loads of mining, manufacturing, farming, ranching. You need lots and lots of infrastructure to be present - even the simple things take a lot of moving parts. Let's see - you want the internet to be present (or it's not really very "cyber").
That means that you need at a minimum, the ability to manufacture computers, routers, string wire across the country, generate electricity, and have enough excess food and water being generated that there's reason for people to work with those things, rather than having to be subsistence farmers.
Let's take one small part of that - stringing wire across the country requires the ability to make high quality copper wire, to manufacture high quality steel (for the towers to hold the wire) and interchangeable parts (nuts, bolts, etc), to manufacture plastic to insulate the wire, and to transport all of those raw materials.
Let's take a small part of that - high quality steel. So to make high quality steel, first you'll need a good source of iron and chromium (to make it stainless, so it doesn't rust through), and you'll need to have developed blast furnaces, which means you'll need a good source of coal for heat (you can use electricity instead, but that just means you need a good way of making lots and lots of electricity, and you can't make electricity without a good power plant, and you can't make a good power plant without steel - so coal has to come first).
So you've got an isolated country that manages to have enough iron, aluminum, chromium, copper, coal, gold, silver, rare earth minerals, etc. to sustain a cyberpunk economy, but remains in isolation?
In short - no. You can be more advanced than your surrounding neighbors to a degree, but you can't have a cyberpunk nation be that much more advanced because by necessity they will need to extend their economy worldwide. If the country is physically large enough to manage to produce all of the possible materials to sustain itself, then it will have to be British-Empire-like in size and scale, and possibly larger.