Please do not listen to @quake. That´s just bunch of rubbish that have no substance in reality. The only thing you need to do is following:
Report the meter stolen at the local police station.
Take a copy of the police report, and visit water company. Tell them that you need a new meter as the previous owner stole the old one.
If they refuse, you just call head office of water company in Bangkok. We have done that, only for things as they turn off water for full days without giving message of ongoing repairs. They fix thing quickly.
The facts are they own the meter, and they are responsible to replace when theft happens. The readings on the old meter, is nothing you should pay. That the is the water company´s job to track down previous owner and collect payment. If you inform Bangkok of that as well, they will solve the problem.