So it's not a company, which means he can't own any shares.
Is the company traded on the Thai stock exchange and are his shares valid or not?
A company that is not trading is not a company at all. I believe the term they use in the UK is 'dormant' and after a period of time being dormant they are no longer companies, I think the term is 'dissolved' but I'm not 100% on that. This is smaller Ltd companies though that are not publicly traded.