Well it's fairly easy.
You can either go on the main 141 website and directly browse, once you find your gem, you can drop her a message to book or go directly there.
But since you are looking for Russians and Thai, I can recommend 3 building/walkup :
- KH Building (King Hing Building) @ Mongkok, basically the whole building is brothel haha. Just go to the top floor by taking the elevator and then walk down the stairs until you find your pearl! (lots of Russians)
- Fuji Building 381-383 Lockhart Rd, Wan Chai/CWB
- JSL Building @ TST (plenty of Thai in this one)
Happy Punt!