If you do decide on paying for an overnight, keep all your valuables in a safe. Some hotels impose a 'joiner' fee, some don't while others don't condone prostitution on their premises. Be sure about your hotel's policies before bringing a boy back.
Don't always expect a 'romantic' night with a gogo boy especially when he can't speak your language. If you're expecting a night of sex, sex and more sex, be sure to tell the boy before 'offing' him. Some gogo boys are married or working/studying and will want to leave soonest.
In a nut shell, convey all your expectations to the boy clearly before payment. Be sure about your hotel's 'joiner' policy. Last but not least, have fun and be safe.
N.B. If gogo bars are not your thing, there are scores of 'massage' places that provide outcall services. Overnight may or may not be feasible in this case. Check with the 'massage' place.
Just visit any of the gogo bars and get a boy. If you want them to stay overnight, discuss this before you off him. You need to pay the bar an off fee and separate tip for the boy. You can always ask how much he wants. Going rate for short time ( few hrs) is around baht1500 and overnight around baht2000. Some boys don't prefer staying overnight, so you need to ask.