What documents do I need to report my 90-day stay in Udon Thani after moving provinces on a dependant visa?

Depending on the immigration office when you move you (or your landlord) is obligated to file a TM.30 form within 24 hours of you taking up residence there. The reason I said depending on the immigration office IS that some offices are hard core about this TM.30 form and some don't care at all about it. Unfortunately on the ones that are hard core about it failing to file it within the 24 hours of you moving results in a fine of 1600baht (usually).

AND seeing as you hold an extension of stay from one immigration office but now live in an area served by another one you should have went and filed a TM.28 Change of address form. Most offices let you file a TM.28 change of address form when you do your next 90 day report.

Notify change of address TM30

and what immigration office will you be using?

... To my knowledge, your new landlord need to register you as the new tenant at Immigration and when he/she did that, you won't have any problems. If you visit immigration for 90-day reporting, and your landlord did not register you as his/her new tenant, then you have to wait until they do ... and a penalty is due to the landlord. It happened to us moving from Bangkok to Pattaya (Chonburi) and at the end I paid her penalty of 1600 Baht because she lives in another province.