Up until February I've always bought them from the Chinese pharmacy in between Soi's 2 & 4 in Sukhumvit - next to Bully's pub. I called in there last month and they were emptying the place - the staff member I taked to didn't know what was happening. The filling station at the top of Soi 4 also sell some papers - they're not Rizzla's and they're so so. I'm told that Villa Market sell them but I've never tried. Another place I was told sell them but never tried is Foodland Supermarket on Soi 5.
If you visit Pattaya you can buy them at the 'Off Licence' for want of a better word on Pattaya Klang road at the junction (traffic lights) with Second Road..............I think its called 'Best Supermarket'.
I usually buy in bulk on Ebay in the UK and take them with me - way cheaper too.
50 Swan Green Cut Corners £8.99 inc UK delivery.
100 " " " " " " £13.89 " " " "
Not sure if Ebay vendors will post to Thailand but I can't see why not. Failing that, I'm over on 1 April and will be staying in Bangkok that night - no problem to bring a pack over for you, I'll be staying in either Lumpini or Sukhumvit.
Don't buy the Thai papers - they don't have glue. I can't work out how that works .