It seems you are from the US, so you apply using the on line system.
For the purpose of visit:
Retirement (pension age 50 or above with a state pension and wish stay inside Thailand for no longer than 90 days there is a insurance requirement of 40.000 Thb outdoor patient and 400.000 Thb indoor patient, which is what most travel insurance offer.
Once inside Thailand during the 90 days you got on entry you open a Thai Bank account, make a foreing deposit of 800.000 Thb, after 60 days but before the 90 days ends you apply for the 1 year Extension of Stay based on retirement and once stamped in your passport, you apply for the multiple Re-Entry Permit so you can travel all you want during that year.
With crazy thinking you could go the other way by visiting the Immigration Office, get the hand out with requirements and apply before 30 Aug for the 1 year Extension of Stay based on employment.
a few copies and application fee are cheaper than doing a border run.
There is no limit on 2 tourist visa each calendar year, I guess you mixed the rule about entry without any visa, named a visa exempt entry by land or sea borders
Depends on what you want, if you entered using a Single Entry Non Immigrant B visa and got 90 days and leaving within these 90 days, you void your stay and can come back using another visa or depending on passport a Visa Exempt Entry or Visa Waiver.
But if you are working in Thailand you need to keep your stay alive as described by Ellie.
Strange idea, but why not apply before travel for the Non Immigrant O visa based on being married to a Thai National, get 90 days on entry and apply after 45 days for the 1 year Extension of Stay.
Non O based on Retirement Visa is actually according the correct terms:
a Non-Immigrant O (other) Visa based on being over 50 years of age and gives you a stay of 90 days inside Thailand, but populair named retirement visa.
During these 90 days you can apply for the 1 year Extension of Stay at a local Immigration Office based on being over 50 years of age and willing to sit out the rest of your life inside Thailand, populair called retirement visa.