Thai Police arrest pedophile Thai Style

According to the Thai Police have in a sting operation arrested four pedophiles in one day. It is a Finn and American and two guys from UK. All of the arrested was in Pattaya and they have charges that can land them in jail for 20 years if convicted. Why the Thai police let this monsters be and wait to they can do a sting operation I have no idea. Would it not be better and save a lot of children suffering if they were arrested as soon as they know about these horrible crimes? I am sure they where waiting for a good day when the big Police boss would come or something silly like that, or when they had no golf rounds to play.