Sort of correct. You don't need any visa, and you get a free 60-day entry stamp when you arrive. Whatever you do when you arrive in Thailand DO NOT follow the "Visa On Arrival" signs, just follow the hoardes
The information being spouted on Facebook is from the so-called "tax experts" who are touting for business. Information from the tax department is contained within the tax code and the relevant DTA
Not correct. Retaining Tax Residency in your home country means you do not pay any tax in Thailand provided your "permanent home" is in your home country. Tax credits only work when you have sole Thai residence but earn money in another country. The DTA provides a tie-break formula which decides residency
Not correct. If the OP retains German Tax Residency and meets the criteria in the DTA, there is no requirement to file a tax return. At the very most a tax residency certificate from Germany will suffice