Thumbs up to the royal thai consulate in HCMC. Non imm O on marriage issued in less than 10 minutes total!!! 5 minutes to submit documentation, and another 5 minutes to collect passport the following day. Make sure that you have all documents required. A list can be found on their webpage.
TLDR : Answer Summary
A user shared a positive experience obtaining a Non-Immigrant O visa for marriage at the Royal Thai Consulate in HCMC, highlighting that it took less than 10 minutes for the submission and collection of documents, provided all required paperwork was ready. The comments included discussions on the process, with some clarifying the need for an approval letter prior to arrival and distinctions between single entry and multiple entry visas.