What are the consequences of using a visa exemption while holding a non-O retirement visa with a re-entry permit in Thailand?

A member of an expat group inquired about the implications of attempting to enter Thailand using a visa exemption while holding a valid non-O retirement visa with a re-entry permit. The discussion revealed that immigration checks are rigorous, and any existing visa details are likely stored and reviewed in their system. Several comments also mentioned requirements for health insurance, especially concerning obtaining a Certificate of Entry (COE), with clarification that the non-O visa may not require health insurance beyond the COE stipulations, unlike the non-OA visa. Participants shared their insights and personal experiences, focusing on the necessity of declaring existing visas and the potential consequences of not doing so.