If you have ever taken home a bargirl, it's 50/50 whether that girl was "underage". The independents, Thai Friendly, farang bars and Thai karaoke will be there of their own volition. Provincial brothels and karaoke may be trafficked or in debt bondage. They'll tell you if you ask. In the old days, brokers used to travel to villages and "buy" daughters to work in 'hotels", "restaurants" or as "maids". May still happen. Again, all you need to do is ask. Thais are honest about their lives. I once paid a girl out of a Baan Sao in Chiang Mai. It wasn't cheap. She went back anyway. I agree, too much age difference is just weird. Look, admire, appreciate, ever flirt and chat, but better not to touch both for her and you.