Yesterday, the national reform council (สภาขับเคลื่อนการปฏิรูปประเทศ) has by a big majority approved the plan to reform the local government units. This plan still has to go through some more bureaucratic steps before becoming effective - it must be approved by the cabinet, then reviewed by the Council of State and considered by the cabinet again, and finally going through the parliament to become a law - but as all these are either the military junta themselves or their handpicked subordinates its quite likely this plan will make it to law in the not too far future.
Prachatai has a long article about this decision, but there seem to be no English sources available. Linked within the article is a scan of the draft law. Being quite lengthy and having lots of technical term I can only get a few parts of the content, the main being section 5 which states that all TAO shall become subdistrict municipalities (Thesaban Tambon), and also states that in case the name collides with an already existing other municipality the one with the highest municipal level or the one being a municipality first shall keep its name. Later sections name the various officials with the TAO, and also the provincial administrative organizaions are mentioned, but my Thai isn't good enough to get any details in these parts.
The massive upgrade of all 5334 TAO somehow resembles a similar steps done in 1999, when all the 980 sanitary districts were upgraded to subdistrict municipalities. The NCPO announcement 29/2016 already prepared for this occasion to allow the current councilors and mayor to remain in office after the upgrade, to avoid massive vacant offices until the junta believes the country is ready to resume with the local elections. I just hope it will be not just a change in naming, but also taking the chance to merge local governments where applicable, so they are able to perform the additional tasks which a subdistrict municipality has to provide to its citizen.