Of course, it seems likely it will be censored if it is shown in Thailand. In fact, when the film was shooting in Thailand back in 2006, the Thailand Film Office tried to get Stallone to tone it down. Picking up on the issue is New Mandela, which offers up this choice quote by Wanasirii Morakul, director of the Thailand Film Office:
Some scenes might be a little bit violent, so we asked them not to make it too violent because if we say that the ethnic minorities are violent, it might be inappropriate.
Now, having not seen Rambo, it's a bit hard to offer any analysis on how it all goes down, but I don't think it was ever Stallone's intention to portray any ethnic groups involved in violence - just the junta - the junta that has traditionally had a cozy relationship with the Thai government.
Hey, if you really want to see it on the big screen, and don't feel like putting up with the Thai censors' annoying nonsense, Rambo is showing in Singapore and Malaysia, just a budget airline flight away. I don't believe that either places are censoring the film - being civilized countries, they have ratings systems. So if you're 18 years old, you are deemed old enough to intellectually process violence, unlike the censorship system in Thailand, where everyone is treated like they are uneducated children.
One Burmese Karen moviegoer in Singapore praised the film for its realism:
Everything is almost - 80 percent - the same as what the movie showed. They rape the Karen people. They kill the Karen people. They just try to kill the village.
Still, Singapore or Malaysia is a bit far to go for popcorn fare. But at least you don't have to wait for the (legal) DVD release.
Meanwhile, Stallone has closed a two-picture deal that could include a fifth Rambo film and a seventh Rocky.