The Verdict: Need More Info
This turns on whether a parent of yours was Thai when you were born, even without Thai papers. Look for your parents' birth certificates and any Thai ID, passport or house registration in the family.
Section 7(1) passes nationality from parent to child with no generational limit, so an ancestor further back counts only through an unbroken line of parents. Papers are evidence, not the test.
Useful sources are your parents' birth certificates (born in Thailand, or registered at a Thai embassy?), any Thai ID card, passport or house registration (tabien baan) for a parent or grandparent, your own birth certificate, and family memory of when an ancestor left Thailand.
If what you find points to a Thai parent or grandparent, take this quiz again. A Thai embassy can tell you what evidence it would accept.