'pi' introduces a modifier of more than one word, as opposed to the basic case that introduces modifiers one word at a time. So in 'tomo pi telo nasa', the modifier is 'telo nasa' "alcohol" as a whole, not just 'telo' then 'nasa' as in 'tomo telo nasa' "strange bathroom" ('tomo telo' means "bathroom")
Now, that compound word can be modified further, so you can talk about your bar 'tomo pi telo nasa, sina'. In this case, the comma is there to show that a new modifier has been added to a phrases that ends in a 'pi' modifier. Otherwise, the 'sina' would attach to 'telo nasa' for 'tomo pi teli nasa sina' "house of your alcohol", maybe a distillery-owned bar, say. Alternatively (and generally clearer), these later modifiers are moved up ahead of their proper place at the end to go before the 'pi' strings, so 'tomo sina pi telo nasa' for "your bar" again. (The commas and the move forward are not exactly official, but if you don't do them you make for ever muddier phrases.)
'tomo pi telo nasa pi laso jelo' is, without comma, a house of green alcohol, absinthe or Chartreuse of creme de menthe or something equally sickening. With a comma, it is a green bar, presumably one painted green (fern bars would be 'tomo pi telo nasa, kasi' or 'tomo kasi pi telo nasa' -- I've never seen a case). I suppose that a green colored bar might also be 'tomo pi laso jelo, pi telo nasa'
Hope that helps rather than confusing things further.