Whether you need to file is determined by whether your income exceeds the filing requirement, not the size of your refund.
For instance, if your only income is Social Security, then you won't need to file a return, because none of the Social Security would be taxable. However, if you have other income, and your AGI is $10,350 or more ($11,900 if you are 65 or older) and you are filing single and not a dependent, then you must file a tax return.
The filing requirements for people who are not dependents are in the screenshot below.
Whether you need to file is determined by whether your income exceeds the filing requirement, not the size of your refund.
For instance, if your only income is Social Security, then you won't need to file a return, because none of the Social Security would be taxable. However, if you have other income, and your AGI is $10,350 or more ($11,900 if you are 65 or older) and you are filing single and not a dependent, then you must file a tax return.
The filing requirements for people who are not dependents are in the screenshot below.