@Johnny *******
seeing as you are already ON a yearly extension of stay there should be no issue at all as long as you can show incoming 65K baht a month, each month, every month for the previous 12 months to a thai bank account in your name only from abroad.
There's no issue changing from "embassy letter" to monthly income method for the following year.
You just have to make sure you don't skip a month, that will run you off the rails for sure 🙂