Thanks! Good analysis.
My main problem with your take however is that you explain very persuasively why NONE of the three main "suspects" stand to gain from the bombings. Therefore, none of them should have been involved, if they're truly rational beings. So I'd say you bring us back to where we started -- not really having sufficient evidence so far to pin the deeds on a specific group.
Let's hope the FBI attaché is already on the case, cabling DC for assistance. With so many bombings (eight and counting), there ought to be A LOT of forensic data very soon. And a good FBI team obviously could help the Thai police to ID the perps.
But if the RTG doesn't want the FBI involved, then one might draw the conclusion that the pro-coup faction were involved. Only time will tell.
Well the insurgents, and I am calling them that because that is what the US military calls them, have a lot to gain depending on the reaction of the Thai government. If this pushes the Thai military into over-reacting then they will gain converts. If the troops in the south just start lashing out, it is going to hurt the governments position. You can not win a counter-insurgency through military force. It has never happened before and is not going to start now. I just hope they are not stupid enough to try.