I'm pretty sure Mai Okumura will play for Nakhon Ratchasima. Okumura's profile page for the World Championship http://japan2018.fivb.com/en/c…yers/mai-okumura?id=68752 and the Japan team page on the Japanese site https://wchs2018.jva.or.jp/team/jpn.html both show her club is Nakhon Ratchasima Mall VC.
No official words from JT Marvelous about Hattaya joining them. I think it will be unlike now because of her knee injury.
I noticed something when I look at Onuma Sittirak's profile page http://japan2018.fivb.com/en/c…s/onuma-sittirak?id=69261, it state that hercurrent club is JT Marvelous (also on the Thailand team page on the Japanese site https://wchs2018.jva.or.jp/team/tha.html).
Oh heck, I thought we had the mystery solved, and that part of the reason Okumura was going to Thailand was to play with Onuma. Do we know how bad Hattaya's injury is? Season ending? I imagine if it involves long rehab she'd want to do it near home.