Karen or simply Long Neck is a name of a tribe from Myanmar (Burma), but also living in Thailand these days.
Karen women are very characteristic, because they wear several metal rings around their necks, wrists and ankles.
You can visit in Thailand villages where minorities live; however usually it’s not so authentic experience and it’s mostly about buying their hand made products (it also can be interesting at some level…).
Golden Triangle is an area where people used to grow opium, at the boarder or Laos, Myanmar and Thailand.
You can visit the place e.g., while being in Thailand, but I don’t really think it’s worth visiting…