No, it does NOT have to be a thai bank. Money from your home country needs to equal 500k thai baht. Different embassy's require different documents though, some want 3 months, some want 6 months of statements. Where are you applying?
You can apply for the initial 90 day Non-O inside the country at an immigration office. You'll need 400k baht in a Thai bank account (but there's no time requirement on it).
This is a group about visas and everything else related to living in Thailand. If you dont want to help someone answer a question then don't, but don't tell people what they should and shouldn't be asking in here. They can ask whatever they want help with.