Anything in particular that you're looking for? I'm flying out of BKK tomorrow so I can check on the prices for you.
The unofficial policy in SIN is that they will overlook up to one open pack of 20 cigarettes...I specifically asked them this the only time (in about 100 times that I have entered SIN over the last 10 years) that I was asked by customs to open my bags. I don't know whether something similar applies to cigars...the only time I bought some in Bangkok a couple of years ago, I just walked through without being inspected.