@Ellie ******
had replied earlier to another Expat....
you have a couple of options.
1. you two apply for Non-O retirement and Non-O trailing spouse in your country together. Once enter Thailand, you can apply for 1-year extension together. The easiest option for timing-wise of your series of applications.
2. you apply for in-country Non-O retirement inside Thailand, then apply for a 1-year extension based on retirement. Once you are on 1-year extension your wife can apply for Non-O trailing spouse at the Thai consulate. So she has to manage to stay until then.
BTW, she can stay on Non-O trailing spouse extension even after she turns 50 if you want.
This is a rough comparison of retirement options.