. What I meant by that was many didn't issue them in the first place regardless so most don't anyway. Only a small amount did. There are 80 embassies here. Op is Canadian so yes , he can.
About 3 or 4 years ago, most embassies here stopped issuing income affidavits, because the thai immigration wanted the embassies to prove the income. Affidavits don't work like that. Embassies were only witnessing your statement of your own income. The onus is on the statement maker that it's true, not the embassy. That's why they stopped issuing them. Some still issue them but most don't.
in that case , you need evidence of international transfer of 40k a month for 12 months into your personal thai bank account prior to applying for the yearly extension. Your bank can provide this in statement form.
Regarding marital status evidence, you need marriage certificate and registration of marriage document. You get both same time when you get married in Thailand. And copies of both signed by you and wife.
Fly to Singapore or KL, turn around and fly back same day. Its allowed as long as you go through passport control there. Most people don't need a visa for Sg or KL.