Scan the documents that that will need to be printed for each subsequent yearly extension, such as your bordered marriage cerificate, passport ID page and contents, house register, wife’s ID, and whatever your local office requires that isn’t a certified or original document.
That way you won’t have to find them each year to print them again.
Your impression may be true or false, a visit your local Thai immigration office should be on your calendar soon to get the correct information from the most knowledgeable people to maintain your legal status in Thailand.
You will need the official documentation stating you have joint custody.
If you used a Thai legal professional for your divorce they should be able to help you with the documents that immigration will need when you get that information from immigration before signing the final decree of divorce.