It is not always as malicious as that. If Thai's have something, they always like to show off to friends & family.
If you an older man, you are automatically the Host same as the West. The difference is that in the West, your lady does not invite all her friends on a date.
But the first time maybe a miscommunication but if you keep paying for everything, without a complaint, they will take advantage and maybe even mock you to her friends.
When you first arrive, it is a celebration (but you pay for everything). You need to make her understand that not everyday is a party.
If you come for 30 or 60 days, they want to get as much as they can. If that is their intent.
I went along with you about being treated like a Human ATM, but it is not always intentional or malicious.
Very common. When I met my girl, at the time, she led me around with her friend's. Next thing I know, I am paying for everyones meal and drinks.
I to had a little conversation with her afterwards. She said she didn't know they were going to do that. Which I don't believe. I didn't speak Thai so I don't know what was said between them.
I have been a guest of older people in the USA and they always pay. So maybe I am guilty of this. Could just be a misunderstanding.
A cruise up and down the River can be pretty cheap but maybe your girls didn't want to offend you with a cheap cruise.
Btw, the river is quite a ways from Sukumvit so travel by taxi down the center of town can be pricey. Did the taxi wait for you during the cruise?