Bitcoin Forum

Guys my friend said that Bitsler is giving free bet commision on chat which is called rains..
Is there any sites like that.

Yes.
In bitvest, you can also receive rains if you're very much active in chat. Just check out this rain (https://bitcointalk.org/index.php?topic=1221154.msg55933683#msg55933683) made nearly a month ago.
There are other casinos that also do the same, check all of them on the Gambling section.

For OP, your thread should be under Gambling Discussion, you can move it by clicking at the lower left of this thread, then select Gambling Discussion board.

As far as I know, Stake.com also has the rain system in the chat, which you can give someone active in the chat section of the particular casino website. This becomes common for every casino platform.

I don't know what sites offer that since I always turn off the chat box while playing since it's a big disturbance for me to see the nonsense chats there, but what I can recommend you since you want free is to go to games and rounds where many sites post their promotion,giveaways and raffles to the lucky users here so it's a good option for you to go since the earnings is quite good for start if you know on what you are doing and also can able to follow the needed requirements ask by the promoters.

windice.io also has exactly the same feature you are looking for. It's been a while since I last used them, but I bet nothing much has changed in there.

I think almost all gambling websites giving away some free coins.
it often happens on Crypto.games casino, plus they have a free coin through the faucet where users can try all games. As I remember, there are many loyalty bonuses, more spent time there, wager, active on chatbox means higher rewards from free coins.