You MUST go to Survarnabhumi ASAP get it sorted. You are now on overstay. If they change the stamp they may hold you and deport you as you don’t have an extension.
Getting a multi entry based on anything but tourism and you can only get that in your home country is like getting droppings off a rocking horse. They want you to get the 1yr extension inside Thailand . They want things to change especially on the financial side and current tax loopholes , we are all waiting to see what happens