Hakika hasn't uploaded the regular battle theme for the thirst update yet, so here it is:
https://files.catbox.moe/xtps6j.ogg
It's a really good remix of this one song from Ghost Path.
https://www.youtube.com/watch?v=DWHQs4m3Ugc

The boss battle theme for the update ended up being this one hakika already posted. Another remix of a Ghost Path song. https://www.youtube.com/watch?v=ffVdBqOHkr4