How can I obtain a three-year business visa for Thailand and establish a branch office for my Australian company?

Sorry if this question has been asked before but couldn’t find anything. I have an Australian company that has a distribution agreement for products made in Thailand. I rent a house as our Thai office but this is not formally registered with the Thai government. I was recently granted a one year business visa for Thailand. The purpose of our presence in Thailand is to assist in design and development and to monitor quality control. We don’t sell or otherwise generate revenue outside Australia.

Questions:

1. Are there any tips for getting a three-year business visa?

2. Would the business visa enable me to start a Thai bank account in the company name or would I first have to register a branch office?

3. Any advice on establishing a branch office would be appreciated.

Thank you in advance.