i got this problem too....threatened them with police(the dude
wasnt frightened)...threatened him with HDB officers(slightly
frightened).apparently he must have been quite skilled with
hammering on someones ceiling in past and got away with it!used
bamboo poles to knock at spot where he was hitting too but things
showed no improvement n got worse1
maybe best thing and only thing to do now is to walk to the
nearest GRC office where you get to meet your local minister of
parliament.they usually have a meet your mp session every week
highlighting grieviences from killer litter to bad neighbours from
hell.
try at your local mp meet your local area mp...make a call...but
i dun think its needed...just walk in at the allocated
times...usually 7pm or something.after telling them your
problem...they would pay a visit to neighbours from hell
upstairs.