I think it is about the cruel business of money, with 'snakes' being used in a slang-ish way; meaning money-obsessed men (or women), eg. "Watching whores parade for the price of fame", which you could associate with pimps or rich businessmen looking for a good time. Also, "Snakes are slithering with dollar signs in their eyes, with tongues so reptilian" supports this. The reference to tongues could refer to how they speak; with wealth-enduced confidence.

Personally, I think it's Gabe's character having to do something (involving snakes... on a plane) that he doesn't want to do, eg. commiting a crime of (possible) vast proportions, kind of like some kind of underground organisation, similar to a mafia.

The chorus hints that it's life-threatening in both ways. If he does it (whatever it is) he could be killed and if he doesn't he could meet the same fate. "Kiss me Goodbye," tells us he's telling someone about it, with somekind of fear almost.

Hope this helps :D