From the BBC article, it certainly sounds like a right old mess of an area, but it would appear that this was a particularly brutal incident even by the abysmal standards of the Mekong River.
I also find it interesting that there was a reference to a gun fight and police seizing the boats. Given the unusual savagery and completely unnecessary execution style killings, as well as the handcuffs on one of the dead, I do seriously wonder if this was a case of especially brutal drug dealers or a spectacularly botched police operation.
Normally, if you went to the effort of tying up and blindfolding your captives, you are not planning on killing them or else you would have just killed them straight away and saved yourself the extra hassle. Blindfolding is an especially strong indication that the captors do not want to just kill the captives as there would be no concern about what the captives might see if you intended to kill them all alone.
Also, if you just executed the entire crew of a passing boat and had all the time in the world to dispose of the bodies, why would you not take off the handcuffs you used to restrain them? Handcuffs are not expensive things, but they are not exactly throw-away items either. Especially since something like that could potentially be traced back to you somehow.
The more details that emerge, the worse this thing stinks.
Given the widespread lawlessness and the savagery of this incident, I do wonder if it is time China pushed for more than just official Thai police investigations. Especially if there is any evidence that Thai police action might have contributed to this tragedy or if there is any hint of a cover-up. But it is hard to see any good options.
Demanding that PLAN or Chinese police patrol boats be allowed to patrol the river will almost certainly not be acceptable to the Thais, and even security on Chinese boats would be problematic as you can bet your bottom dollar that you will have bleeding hearts or people with an axe to grind putting grief stricken family members in front of the cameras crying about how Chinese soldiers killed their beloved son even if that son was killed because he tried to hi-jack a civilian boat with an assault rifle.
Drugs is not a problem the military can solve. You need solid law enforcement presence on the ground providing security and plenty of develop money and viable alternatives for farmers. That is going to cost a lot of lives and coin, and I do not see the Thai government having the capabilities or stomach for the kind of measures needed to root out the problem.
Somalia only got broad international support because western ships and crews were being taken. As long as these animals don't go executing a boat load of westerners on the Mekong, the world won't give a crap, just like it doesn't give a crap about how many Mexicans or Columbians gets killed in their drug wars. Any attempt by China to protect it's shipping and civilians will be portrayed as 'bullying' and 'expansionism' by the usual suspects and gleefully lapped up by the western media.
I think China is playing the best card it can at the moment - economics. Suspension of all Chinese shipping is going to hit a lot of people hard in Thailand, especially if it lasts any length of time. Nothing gets action like hitting vested interests in their wallets. Although the risk is always that the local police will just round up some scapegoats to execute to 'resolve' the situation and the real culprits are never brought to justice and are free to do this kind of savage act again.