Sometimes there is a big bell hanging from a chain or rope in the bar near the register. If you ring this bell that indicates that you want to buy all the girls in the bar a drink or maybe everyone in the bar for a drink.
If you want to get attention to yourself and be a showoff and let all the girls know that you a generous guy, this is one thing you can do. right away all the girls will be alot more friendly to you and the mamsan will be your best friend that night and ll the other nights you show up at the bar. This could run you about 1,000 bht. Merely a small chunk of change compared to a bar abroad.