Whether the thesis will be spot-checked after graduation depends on many factors, including school, education bureau, academic ethics and so on. Generally, papers will not be randomly selected after graduation, but there are several situations that may lead to papers being randomly selected:

Academic misconduct is reported: If others report academic misconduct in your paper, such as plagiarism and tampering with data, your paper may be randomly selected.

Involving sensitive fields or major errors: if the paper involves sensitive fields or has major errors, it can be randomly selected by higher authorities or academic institutions.

The school or education bureau needs spot check: if the school or education bureau needs to check the graduation thesis, your thesis may be spot check.