Do bounty participants have to pass KYC procedures?
Yes, they do
Which docs should I provide?
Passport or any ID would do just fine

Also, you should provide your selfie holding it
I have double citizenship US and Thailand. Can I participate, because I know, that us citizens cant participate...
Yes, just use Thailand passport for KYC

You finally got me confused...
If I am send docs not from US I must use passport only or Thai driver license would do?
Yes, you can use your Thai driver license

However, please, note, that it may change
Also there must be duplication of your name, surname and all needed info in Latin letters (Eng pronounced)