Firstly, whatever is said on this topic you should go to a lawyer and other specialists
"I am looking to buy a bar in north of the country"
To get a non-B visa, you will need a Thai company. I'm assuming you're attempting to buy an operating business, in which case you've got that box ticked however you will want to speak with a lawyer before purchasing as other rules will apply depending on your level of investment etc (Thai directors and Thai employees etc)
You won't have to apply for a work permit, it would be recommended that you DID. With just the visa you would not be allowed to "help" at the bar in any way what so ever (legally).