What document do I need to prove I've never been married for marriage registration in Thailand, and which agency in Minnesota can help?

To prove you have never been married for marriage registration in Thailand, you typically need a self-serving affidavit, which can be obtained at the US Embassy in Bangkok or the Consulate in Chiang Mai. In Minnesota, the Bureau of Vital Statistics can provide guidance on marital status documents, but Thai authorities may not accept documents from the US directly without notarization at an embassy. It's also recommended to have supporting documents, such as divorce papers if previously married.