The fact that you have already had a retirement visa will be a red flag you have already demonstrated that you are not a genuine tourist, first time you will be questioned about your intentions thereafter you may be denied entry or at least given a final warning and flagged on system……better to just legitimize your status,
the many spoil it for the few, the warnings are out there now, folks should heed - the ETA can’t come soon enough and that will put a stop to the systemic abuse of Thai hospitality. Try getting into AU/NZ/US without correct visa……