In trying to learn the Korean language, I've come across a few differences in Korean translation. Can someone please clarify which Korean text I should be learning from?

Gamsa is really informal like if i had a friend the same age as me and we are good friends or to someone younger than me.
gamsahabnida is the formal way of saying it. that’s to an elder or someone you just met etc…
the in between so to speak is “goh mah woh” but that’s still on the informal side. it’s better than gamsa but still considered informal. best bet: gamsahabnida. you can never go wrong with speaking to someone formally.

In my travels through Korea everyone said Gamsahabnida. As @uberbatman said, go with formal 99.9% of the time.

Also, stay away from Soju. It can potentially make everything entirely too informal.

With regard to gamsahabnida/kamsahamnida, I suspect that there are just different ways of representing Hangul with the Latin alphabet, as it would be difficult to represent it accurately. If in doubt, go by the one which you’ve found most often.

I don’t think either spelling is Revised Romanization, the official romanization system of South Korea. In Revised Romanization 감사합니다 is gamsahamnida.

Quite often the “g” that you see is really pronounced more like a “k”. The government’s “official” system is quite a bad representation of the way Korean truly sounds but it is the one you will be seeing most often.

@garydale My understanding is that the Revised Romanization is not meant to approximate pronunciation. It’s meant to be a one-to-one transliteration. That is a symbol in in the Roman alphabet corresponds to a symbol in the Korean alphabet (but it doesn’t quite achieve that). But if you learn the system then you know how to pronounce it.