Refuse To Be A Victim!
The best way to deal with Thai bargirls and others as you quite rightly say is do not let them know too much about yourself from the start of any friendship including where you work and live. One always has to be alert with these girls. It does not matter if you holiday in Thailand 2 or 3 times a year and meet up with the same group of lady friends each time you visit, they are always lying or trying to scam you.
I have been coming to Bangkok 4 times a year for 10 years and have met and kept in contact with many beautiful girls (many of whom do not work in bars but frequent Spasso's, CM2, Q Bar etc. – freelancers, I guess) and the stories I get are amazing but I have heard them all before. One will note that they send a few SMS before you arrive in Thailand but these dry up when you leave until the next time. When you send them an SMS when you are back home and they do not reply the excuse is always "my phone is broken" or "I left my phone in a taxi" or "no credit in my phone". We've all heard these excuses before. Funny thing is I was seeing a beauty from Spasso's for around 1 year off and on and when I was over in October I arranged to meet her in a bar at 10 in the evening. We had a few drinks and then she asked me for some money. As I had just started my holiday and was flush with cash I gave her 5000 baht. Guess what? 10 minutes later she was gone out of the bar and left me and my friends wondering what had happened to her. No goodbye, nothing. Talk about embarrassing in front of farang friends. I did not speak with her again for a long time and indeed I saw her at Spasso's on another night with some other farangs acting towards them the same as she had always done with me. I felt sorry for the farangs she was with and nearly went over to them to warn them about her but I thought that they probably know her ways already.
One thing any farang on holiday should do is never tell anyone when they are leaving the country. If you are due to leave on the Sunday and you tell the Thai lady you are going on the Sunday she will try everything to get your cash on the Saturday before you leave. If the girl is a rogue your gold will be nicked on the Saturday. Always tell them lies like I am leaving on Sunday for 3 days and will be back on Wednesday or I am leaving in 5 days, when you are actually leaving in 2 days. Always drop hints that your friend is a lawyer or your brother is married to a Thai policewoman and you cannot see her tonight as your brother is coming to dinner with his police wife. You have to keep one step ahead of these girls as they know their manor and are well used to conning tipsy farangs looking for a good time when on holiday. I know that many of my mates who live and work in Bangkok always say there are a lot of good spare girls in Bangkok but it is difficult for anyone on holiday having a bit of fun to get a date with a nurse from Bumrungrad or a girl from the Chanel counter at the Emporium. We are left with going to Spasso's, Bed Club etc but believe me there are also a lot of good looking, smart dressed farang guys also chasing the good looking girls at these clubs and it is my honest opinion that the best looking of these girls are making a mint being taken care of by farangs and farang businessmen who frequent these clubs. If a farang businessman is staying at a posh hotel in Bangkok and enjoying a drink at a posh club and is approached by one of these Thai babes it is almost certain that guy will have a bit of fun on their expense account without anyone but him and the girl knowing. You just have to look at how many airline pilots, bankers, government officials etc have frequent stopovers in Bangkok and where they stay.
If you are a very good looking Thai girl between the age of 20 and 35 who speaks good English and dresses well the chances of making good easy money frequenting the right clubs will ensure you are going to make a good living for many years. It is probable that you may have 3 or 4 farangs on the go at any time and if each of those farangs sees you every 3 months and each guy blows 20,000 baht on you each time they are in town that soon adds up to a lot of good dosh without taking into account the money you make freelancing when your farangs are not in town.
A tip, if you are a farang that likes to play with more than one girl, stick to girls from classy bars, at least if you do fall out with the girl or she robs you it is possible to go back to the bar the next night and track the girl down. Most bar owners do not want bad publicity brought upon their bar especially if the bar is farang-owned.
Finally if you can afford it always have 2 mobile telephones Only let the girl know your private number. Never let the girl know the number of the phone which your wife answers or who may pick your mobile phone up when you have been sent an SMS from a Thai girl you met whilst in Thailand. It is almost certain to cause a hell of an argument or worse. I once received an SMS from a girl I knew called Pom. The SMS asked how I was doing and when I would be in Thailand again. My wife picked up the SMS when I was in the supermarket and when I got back to my car she asked me sternly "Who is Pom?" I did not know what to say and was terrified. I finally confessed that Mr Pom was the manager at the Omni Tower in soi 4 and always sent an SMS to enquire when I would next be in Bangkok. It worked once but I doubt I could make up that excuse again in a hurry.
Lots of good advice here!