Does anyone know what it takes to get a Non B (1 year),when applying in Brisbane.Basically I need a letter for a local Thai company stating they consider to hire me,but can it be just any company ?Is anything else needed besides of that letter?...

As for the Non B visa itself ,does it allow any kind of flexibility with doing jobs here? Can I do any kind of trial period job/consulting?

No visa allows any work. You must have a work permit to work and that requires a Thai company of some type that can support the issue of a work permit. It is specific to job and place. Can not answer what Brisbane will require.

Would suggest you give the consulate a call. You will need a letter from Thai company for sure, but the consulate may require sight of other paperwork too. As Lopburi says, you will also need a work permit from the ministry of labour to work in Thailand which your employer would help obtain as your sponsor.