The short answer is “no”. SSI, which stands for Supplemental Security Income, is not the same as Social Security Disability benefits. This program is not funded by payroll taxes as Social Security Disability and Social Security Retirement are. Funds for SSI come from general federal taxes. However, the fund is administered by the Social Security Administration and the person must be disabled per the Social Security disability guidelines.
SSI is a “needs” based program. That is, it provides a monthly benefit to those disabled individuals who have not worked a sufficient amount of time to accrue credits towards Social Security Disability benefits and who have very few assets. It is, in fact, a poverty program for disabled individuals.
If someone is getting SSI benefits, at age 65, their benefits will automatically convert their from disability to “aged” benefits. The benefit amount would not change. At 65 these individuals, who have been receiving Medicaid benefits would convert to Medicare benefits for their health care coverage.