It seems a host bar has just opened in Rayong.
It is called "Baan Chai Num" and is located on Soi Hotel PMY, they have also karaoke and some dancing. Off fee is 200 THB, they have both part-time hosts and regular hosts.
Never gone there (I am presently stuck in a boring place 9500 km far from LOS) but got this information from a thai-speaking forum :
Rayong bar
At this link you will find the phone numbers.
If you go there please send a review as I never saw this place mentioned on any farang-oriented site.
On another website someone pointed out the bar located in the basement of the Rayong Orchid Hotel which would have boys for rent ...
Have a good trip !