nylon is the basics. i dont know specifics about nylon, all i remember is that nylon can run you $15/yard. and dont expect to find the fabrics at your local joanns or fabric store. consider online retailers.
seam sealing is generally done with tape. it always has seemed like electrical tape that has been treated and heated, but i can guarantee you that it is something more.
thread could be either regular thread or more filament like thread.
question regarding your venture. do you have a sewing machine that can handle this task. most consumer sewing machines found at michaels, joanns, ac moore cant handle this, even if a retailer says so. in general you would need a industrial sewing machine - one that sews boat tops/covers, or actually from a textile shop.