Business visa and work permit are two separate things, issued by two separate government bodies... but you need both to be legally working in Thailand. It's best to consult an expert on this matter rather than asking it in here.
Definitely due to China opening up. However the reintroduction of this requirement to enter Thailand is still in proposal stage and not official yet. Apart from proof of vaccination, they might bring back travel insurance which covers Covid as well.
Imagine they allow foreigners to buy land and 6 months later, the rules change and foreigners that own a land in Thailand must sell their land within 3 months or will have to forfeit it. Guess how much locals are willing to pay for that piece of land owned by foreigner? 30% of market value? 🤣🤣🤣