Not sure where you’re from but in uk where I’m from when you renew your passport they send you the old one with cut pages to know it’s out of use so you should be fine 👍
You’re ok as there is a Germany - Thailand double tax agreement which prevents you from paying double tax. You can continue to pay tax regularly in Germany 👍
It’s possible as an investor. But there are many coffee shops in tourist areas I have a friend who opened a coffee shop and struggled due to high competition. Whilst there are also many, I have heard visa / tourist businesses can be profitable with the right staff. Good luck 👍
If you can demonstrate an income of around $85k and proof you can complete work remotely you at least have a decent case but I would speak with a visa agent for more info mate