From ladies I have talked to, both in Thailand and the US, it is not uncommon for ladies to work in the sex industry to support the family back on the farm. I have been told that the boys/men aren't responsible for that and that the family doesn't ask where the money comes from. In a bar in Thailand I am pretty sure of their occupation but at a non-bar or a party if they tell me they work in a restaurant, or office, etc., I have no reason to doubt them.
As to fake id it seems that it is readily available in the US for high school kids to buy alcohol. Most convivence stores and liquor stores are run by non-native people who aren't particularly fluent in English but are anxious to sell their inventory. I find it highly that it is difficult to believe fake id is more difficult to obtain in Thailand than the US. Also if the operator of business in Thailand (where there is no prostitution ????) doesn't know how to get fake id for underage ladies, whether Thai, Cambodian, Malay, or.... The story also seems to indicate that these ladies were brought to these men's rooms. I don't remember whether at a hotel or in a room attached to the bar establishment. If in a hotel, I understand that the hotel is required to inspect the id of anyone to rent a room, and anyone not registered.
All from that aside, I do believe it is difficult to be blind to a female under the age of sixteen unless that is what you are looking for and that is creepy, IMHO, if not reprehensible! I know how shocked I was to see a very young lady at a boat party in the US sitting on a on man's lap who seemed to enjoy beer more than the gym. I asked a friend what that was about and was told that it was his 22-year old daughter and she had been traveling around the world for more than a year. There is also the fact that it is fashionable to have a bald pubic area which I was surprised at until later when I was shown some Playboy mags.