You may be lucky with the massage but it is not usual. Choose a place that doesn't look busy.
Alternatively, a good brothel, from the bottom of Pub Street (end pointing direction of airport), turn right (direction of monuments) and take first main road left. There's a brothel a little way down on the left hand side. Only a few availables inside but pretty laid back and cheap. If you are more adventurous, carry on down that street (it gets dark, but not a worry) and take the first main right. After a hundred yards or so there's a big disco joint on the right with chicks and guys hanging around outside. Carry on past there and there are small side streets to the left mostly run by dodgy Chinese. Facilities are basic (more basic than the first one I mentioned earlier) but more choice and possibly more talent. It may have changed since I went last but it's been like that for many years over different visits so possibly or probably still more or less the same.
The big disco down a side street parallel to Pub Street is pricier but an open brothel with take out. The bar in Pub Street with lots of pool tables is the easiest place to pick up a reasonable looking part-time freelancer (you have to haggle hard). The street itself has grabees (chicks that seem to grab and hang on to your shirt sleeve wanting to fuck their ugly bods) are overpriced but will usually take you back to their shit-hole of a habitation (you wouldn't want to walk into any reasonable hotel with them). If you get stuck, there's an Ozzie guy that runs a mid-range hotel in the north of the city, a tuktuk from Pub street, the Golden something-or-other, and he used to invite agreeable tourists to accompany him and his wife pussy-hunting downtown. If he doesnt still do it, his place is still a good bet for a first rate tuktuk or moto driver when you wat to go a longer trip.