As Jingthing correctly points out you do not need to be in Thailand for any length of time, however in order to renew your extension you would need to be in Thailand at the time prior to expiry.
Your plan with both extensions to a non O retirement OR using tourist visas and visa exempt entries for about 6+ scattered months in Thailand and balance of time in other countries will work fine.
If money is no issue and keeping funds in Thai bank account all year not a problem then the extension to non O with reentry permit allows you easy access to Thailand throughout the year.
With the reentry permit you have zero issues with airlines.
FWIW, I would like the luxury of having a 12 month permit and be able to nick off to anywhere anytime.
Like your plan.