You must show that you do not have interest in overstaying, show you can afford to travel, not need to work to support you trip.
1 have job that pay a decent wage show funds deposit regularly
2 have resident property under your own name
3 have fat bank account for 6 months and longer.
4 no relatives in the state which can provide shelter and job. BF or GF should show regardless of approve or not, it will enter into evidence when you apply for a fiance or married visa.
so go retirement visa, renew year by year, Enter visa waiver , apply within country, there an agent do a visa run for less than $200 plus cost of visa.
No need to leave the country.
And when you have 800k THB balance in the bank, you don't need the SSA statement.
Assuming you have US passport, just buy tickets, fly, go to immigration, ask for a letter of permission to open bank account, state your intention to apply for retirement visa. Then go to Bangkok Bank, open account, deposit 800k thb minimum.
I recommend after open account, get an agent to help you file for the visa( knowing someone in the immigration help speed thing up.)an agent can cost you around 5-8k thb.