learning a spoken-only language

[Axon]

I think the first steps are understanding what you want to accomplish as an outsider learning this spoken-only language, then making sure you've truly exhausted all existing resources.

When you imagine yourself comfortably using this language, what are you doing? Are you regularly living in that community, are you chatting with people every so often, are you raising a child to speak it, are you living with a monolingual speaker, are you exchanging pleasantries and then switching to another language...? This could give you direction toward the recordings and dialogues you want to create and learn from.

There are actually many existing resources for Sgaw Karen, as minority Southeast Asian languages go. You said that the vocabulary you were learning was different from that of the speech community you're interested in. Did you check out Google Scholar for papers on different dialects of Sgaw Karen? I've had luck on Fiverr contacting recording studios in China who are able to source native speakers from surprisingly small dialect communities, though that was very expensive. Are you able to join any group chats where people might be sending voice messages in that dialect? Could you get a core word list (from a scholarly paper or from Youtube) and then work with a native speaker to help you understand what words are different in your chosen dialect?

In fact, the choice of dialect might be influenced by your ideal role in the language community. In some communities, it would be normal for an integrating outsider to speak a version of the local language with a distinct accent or influence from either the majority language or a prestige variety of the minority language. If you learned to speak textbook Sgaw Karen (referring for example to the works published by the Thailand Karen Baptist Convention) and learned to understand the variety spoken in your chosen language community, would that be socially acceptable and help you meet your goal?