Where in Bangkok can you get a half decent girl for 1000? In my experience even street freelancers are 2000 or more!
But as we have said, it does depend on your activity- but remember if you only get one girl for short time , what else are you doing in the day and evening- tourist stuff costs money etc
Op - yes you can do it for less particularly if you are younger ( not an oldie) but if it’s your first time in Bangkok, then you want to do some tourist stuff as well as some punting stuff so imo, allow a minimum on 5k per day and as previously said, a 10k per day budget allows you to have non stop fun!
I would add that if you are there for more than just a couple of days , then think about going to Pattaya- it’s only 2-2.5 hours taxi away (c1500baht) and the fun and prices there is a lot better!