BGs like to have a good time and they expect to be paid for it. If they like you, they will be happy with 1000 Baht. If not, they will ask for more. Unless they want to get more than 1000, then it would be quite rare for them to bring up the subject of money. They just assume that if you are not a big jerk or just stupid, that they will get at least that. They know and you know that 1000 Baht is a pittance to most farangs, so why wouldn't you give it to them? They may not ask, but it is what they expect. Do you also go to a restaurant and not tip the waitress because it is not required, and they don't ask you for a tip? I think I know the answer to that question already.
If you are with a good-looking BG, and she doesn't ask for money, then it usually means she likes you, and would rather go with you than some other guy. But like the waitress, she expects you to show some appreciation for her "services"(your word, not mine).
BTW, you can not take a BG out of a bar, unless the BF is paid. Do you expect them to pay the BF for you? It is usually only the cost of 2 or 3 drinks. Can't afford it, Charlie?
The key word there is random. When you go to a ladybar, that is not a random meeting. The bar is a place of business where girls go to find customers.
On my 1st two tours, in Patong, I hung out with a young Greek guy I met at breakfast. He was friendly and spoke English well. He was also very charming, good-looking, great smile, and well put together. He was obviously a ladies man and all the BGs swarmed to him like bees to a flower when we went into the bars and he had his pick of the girls. But, he told me, that he never paid for sex, as it was against his principles. So he would usually have the best-looking girl in the bar, hanging all over him, smiling, and trying to get him. He would play with them for awhile, joking around, flirting, and had them wrapped around his little finger. BUT, after he had amused himself for awhile, then he told them that he had no intention of paying them, that if they went with him, they would get nothing. Guess what happened, every time? When they realized he was serious and not joking any more, then they immediately switched to me, who was willing to pay them. I would just brush off the other girls and drink with him, and the girl after him. Then when she realized he wasn't paying, she was mine for the night. That is how it usually went. Not one single time did a girl tell him, oh, that doesn't matter, I still want to go with you. He bought them drinks and sometimes would even give the flower lady 500 Baht for her whole armful of flowers, and give them to the girl. The girls were blown away by that, and thought they had found the perfect guy, very handsome, young, buffed, charming, and generous. Then he lowered the boom. They would look shell-shocked!! Just couldn't understand why he would pay 1000 Baht for drinks and flowers, but was not willing to give them 1000 Baht. But not a single one offered to go with him or free. He did, however, have very good luck with shop girls and hotel clerks, and European/American/Japanese girls on holiday.