The K-1 visa, also referred to as the fiancé visa, is a non-immigrant visa that enables a foreign national's fiancé to enter the country to wed their American citizen petitioner within 90 days of arrival. Here are some details on the Thai fiancé visa:

1. The petitioner must be a citizen of the United States, and both the petitioner and the fiancé(e) must be of legal age to marry in order to qualify for a fiancé visa. Before submitting the visa application, they have to have actually met in person within the previous two years.
2. The petitioner, who must be a U.S. citizen, must submit a petition to the U.S. For their fiancé(e) in Thailand, they need to contact Citizenship and Immigration Services (USCIS) to get a fiancé visa. The petition is authorized, and then the U.S. receives the visa application. The fiancé(s) must apply for the visa at the embassy in Bangkok.
3. Required Documentation: A police certificate, a medical examination report, and proof of the fiancé's (e's) relationship to the petitioner are among the papers that must be submitted to support the visa application. Additionally, the U.S. citizen petitioner must submit supporting paperwork, such as evidence of funding and citizenship.
4. The fiancé or fiancée must appear for an interview at the United States embassy in Bangkok, where a consular official will question them to ascertain their eligibility for the visa.
5. Processing period: The duration of the fiancé visa application process varies; however, it usually lasts several months. The fiancé(e) must enter the country within six months of the visa's issuance and marry their U.S. citizen petitioner within 90 days of arriving.
6. The fiancé(e) must apply for permanent residency (a green card) after being married in the United States because the fiancé visa is a non-immigrant visa.

In general, the fiancé visa gives American citizens and their foreign fiancés a way to live together in the country and get married. However, the application procedure can be complicated, so it's crucial to carefully adhere to all the guidelines and supply all the required paperwork to prevent delays or the visa being denied.