Not getting "The White Elephant" achievement. Am I missing something?

[Azhcristokos]

So I'm playing an Ironman game as Ayutthaya. I know achievements are enabled because I've gotten a few achievements already. Recently, I finally annexed my vassals and have united Indochina and I now have state cores on every province in the region. However, The White Elephant achievement still hasn't fired.

Am I missing something obvious? Is there some random island I need to get or something? I've checked and as far as I am aware, I have every province in Indochina. Is there maybe some other requirement I'm not aware of? Or is this maybe a bug?

I've uploaded a region map of Indochina and a political map of the region as well. My apologies if there is something obvious I missed, but I appreciate any help you wonderful people can offer!

 

[ArzhurG]

You seem to be missing some of the provinces in the Burma region. You need both the Indochina and Burma region as per the wiki.

 

[atwix]

the requirements for this achievement have been misleading ingame since ages....

yeah, you need burma region completely also.