What happens to my 90-day Non-O visa if I leave Thailand and return using a re-entry permit before the 90 days are over?

The consensus is that if you have a Non-O Visa with a single entry and you exit Thailand using a re-entry permit, you will not receive an additional 90 days upon re-entry. Instead, your stay will only last until the original 90-day period you were granted upon your initial entry. Therefore, you cannot extend your stay beyond the initial duration even when using a re-entry permit.