Anyway, just today the page on the Thai provinces at statoids was updated, adding one sentence to it.
Update 6 to "Geopolitical Entities and Codes" is dated 2011-11-30. For Thailand, it assigns a FIPS code to Bueng Kan province.It turns out that the National Geospatial-Intelligence Agency of the US military - the same agency which was responsible for maintaining the FIPS 10 standard - continues to maintain the codes of this former standard under the name Geopolitical Codes. In fact, without the bureaucracy of the National Institute of Standards, it issues many more updates in a more timely manner. The latest update 6 from November 2011 now adds the code for Bueng Kan, 10 months after it was created.
THAILAND (FNC 369)Unlike the previous changes in the FIPS codes, this time the province which was split did not receive a new code - e.g. Udon Thani changed from TH19 to TH76 with the creation of Nong Bua Lamphu. So I would have expected to see Nong Khai receiving the new code TH82 with this change.
TH81 Bueng Kan
The latest newsletter with updates of the ISO 3166-2 list from December 2011 still has no mention of Bueng Kan however, even though they just need to copy the code from TIS 1099. Or to be more exact the working copy by the Ministry of Interior, as there was no update for the Thai standard since 2005.
I sent an email to the National Geospatial-Intelligence Agency if the retaining of the code for Bueng Kan was intentionally or not, and today received the answer that it was in fact intentionally and a change in the policy of handling the splitting of subdivisions.