Are you still stuck on this?
Not played the version you mentioned but it looks like the usual method, you need to find another way around to get to Lavender Town, acquire the Poke Flute Radio Station and then return here, set the Radio up playing the Poke Flute and then engage Snorlax. Hope this works, like I say, I've not played this particular version but this is the usual method in the usual games.