Rahaf Mohammed al-Qunun told AFP she ran away from her family while travelling in Kuwait because they subjected her to physical and psychological abuse.
The 18-year-old said she had planned to seek asylum in Australia and feared she would be killed if repatriated by Thai immigration officials who stopped her during transit on Sunday.
The incident comes as Saudi Arabia faces intense scrutiny over the shocking murder of journalist Jamal Khashoggi last year, which has renewed criticism of the kingdom's rights record.
Thai immigration chief Surachate Hakparn had said Sunday that Qunun was denied entry because of her lack of documents.
But he made an abrupt about-face the next day, following a global media frenzy as the young woman pleaded on Twitter for different countries to help her.
After announcing that Thailand "will not force her" to leave, Surachate told reporters late Monday that Qunun would be "allowed to stay" after a meeting with officials from the UN refugee agency UNHCR.
