No, South Korea is only consistently competing in dressage for some reason. India could be Thailand's biggest victim, though.
I guess we will have to wait and see about Thailand. This is an incredible opportunity for them, so I wouldn't be surprised if they started investing more. Maybe their previous Olympians from 2004 and 2012 will make a comeback (similar thing happened with Japanese dressage in 2016, when a whole lot of semi-retired athletes came back following the surprising qualification). But in any case, Thailand will be working on a very short time frame.