A residence Certificate is only valid for 30 days from date of issue by immigration. It is commonly used for opening bank accounts, buying/selling vehicles, getting a license.
If you are retiring in 2 years whatever the rules are now could possibly change, 2 years is a long time in Thailand,by all means look into the rules now, but by the time you apply the have probably changed. There are possible upcoming changes in the wind for next year, just follow posts and websites to keep abreast of it all.