What are the financial requirements for applying for a Non-O visa from London?

To apply for a Non-O visa from London, the common misconception is that you need to show £18,000 in your bank account. However, the actual requirement is to demonstrate 800,000 THB for a one-year extension or a lower amount (around £10,000) if your application is based on marriage or having Thai dependents. Some commenters suggest maintaining slightly higher amounts in your accounts to account for exchange rate fluctuations.