Dear fellow smoking traveller,
If you know what the customs bond facility at Changi Airport is then this post might be useful for you.
There has been discussion on TA regarding customs bond services at Changi Airport, i.e. you may avoid paying taxes for dutiable goods such as tobacco and alcohol when "transiting" through Singapore.
This service is no longer offered by customs as of February 1st. Unfortunately this means that if declare you tobacco you will be offered the option to pay taxes or for the items to be destroyed.
The tax for a pack of cigarettes is 7 SGD, cigars are taxed by their weight.