@Kristen *******
Also Canadian and over 50. We entered in October on 90 day Non O. We did the one year extension based on retirement, with me as a trailing spouse. As Canadians you don't have to season 800K THB in an account, you can get an income verification letter from the local Canadian Embassy or Consulate. You need to provide your summary page from you last tax return which must show earnings of over 65K THB/month. You can download the form from CRA.
Not sure if that's possible in your situation based on your spouse being from Hong Kong. Should probably work for you though. I believe (?)you can do a trailing spouse with the 800K THB deposit but you'd need to confirm that.
We were told that in order to do a trailing spouse we both had to enter on a Non O, so we applied before coming to Thailand.
We dealt with the Vancouver Consulate and they were very helpful. PM if you have any questions.