ETA will eventually replace TM6 in all likelihood, baby steps, which makes sense, ETA is a big change especially with upgrade to electronic gates replacing immig.
the TM6 has never left the royal gazette……they just decided to waive it for a while after Covid perfectly entitled to now remove the waiver without approval from Germany, even if it is now automated in preparation for ETA…which probably would have to be gazetted along with B300 tourist fee….
only if you apply for Non O-A , better to apply for O visa on line in home country then the retirement O visa when you get here provided you can show the 800k in Thai bank….