why? The process is come to Thailand get non o visa and apply for 12 month extension of stay, leave if u want and come back just get a re-entry permit.
I have 12 months extension of stay, it very complicated on purpose it encourages us to use an agent to help. Essentially come to Thailand and do it from there. Remember if u are in TH for 180 days its very likly yoiu will have to pay Thai tax.
Difficult these days to open a bank account, with the new visa classes has got even harder to understand. Most people use agents to get what they want. For the future remember that you will need to pay income tax in Thailand, new rules.