I have been running a business services company since 2002, specializing in providing incorporation services, and assistance with work permit and Immigration processing to foreign clients seeking to operate businesses in Thailand. So - I know of what I speak.
Comparing Immigration processing for extensions of entry permits based on marriage, and based on retirement:
Advantages - If based on bank balance, need only maintain 400,000 baht minimum balance for 60 days (initial) or 90 days (renewal). In this status, you ARE permitted to work, with work permit - and as long as you have a previous tax year form PND.91 (personal income tax return), your employer may sponsor an extension your entry permit with just 1,000,000 baht registered capital, and two Thai employees (versus 2,000,000 baht registered capital and four Thai employees, if you do not have a Thai spouse).
Disadvantages - Requires substantial photographic evidence of "happy couple at home". Wife must appear with you at Immigration once per year. If you were married outside of Thailand, requires substantial bureaucratic certification of foreign marriage certificate. Processing involves a 30-day "under consideration" period, before receiving final "one year" extension.
Advantages: Approval of one-year extension occurs on the spot - one-day processing.
Disadvantages: You may not work - not eligible to apply for work permit if holding Class O retirement extension. If extending based on bank balance, requires minimum balance of 800,000 baht for 60 days (initial) or 90 days (renewal). If extending based on pension, requires certification of pension by your country's Embassy in Thailand.