Thai Ladyboy Questions

[Dong]

Just wondering when I am in Thailand looking for ladyboys, how do I know for sure. I hear they are quite passable there.

Questions:
1. Do they announce that they are Ladyboy, or do they sometimes string you along thinking they are a girl?
2 Other than visual inspection of the bare package area, are there any tips on how to distinguish them before I hit on them?