Brunei Visa - the Conspiracy
A permit or visa doesn't guarantee entry since it's the immigration officials discretion if you're in a position to step in a foreign land or not. It is also feasible to be granted a visa if you're traveling during an important festival period. Visas are valid for a couple of years, but can be readily renewed if you opt to stay longer.
As an example, citizens of GCC nations need not apply to get a visa to go to Dubai. You might also be banned if you've breached immigration laws in the Bangladesh. Some countries may just provide a single entry, some might only provide single or multiple entry, and others might just provide multiple entry visas.
Officially it's the Brunei Dollar, but you could also use the Singapore Dollar that's fixed at precisely the same rate as the Brunei Dollar. If you are only visiting Brunei for a quick time period you might not require a visa. Malaysia is also among the most developed nations in the region, with permission from Singapore and Brunei.