Ask your embassy if they issue income verification letter. Canada does so I use that method of making over 65 K a month. It’s so much easier than letting 800 K sitting in a bank account doing nothing. My embassy charges $50 cad.
Oh and do everything yourself. It’s very easy to do. 1900 Bhat at Thailand Immigration
How long do you want to stay here? It’s easier to come here on a visa exemption and then apply for an extension of stay based on retirement. Email the Canadian embassy for a verification letter of income. Costs $50.00 Apply for the extension here in Thailand yourself. 1900 Bhat. Super easy to do. No insurance required (but good to have).