A better summary: the Thai powers that be have no respect for silly ideas such as democracy, justice and human rights. They think the ordinary Thai need to be obedient, need a strong leader and those who step out off line need to be punished (severely I may say: abduction, torture and killing are on the menu).
Thailand has a history of critics disappearing or being murdered. Just read T. Habekorn's book 'In Plain Sight: Impunity and Human Rights in Thailand'. Your life ain't worth much in SE Asia if you advocate democracy, human right or anything that hints at a republic. This poor chap probably is dead already, buried or floating in the Mekong. Who's behind it? Good question but the list of possible suspects ain't large . Poor unfortunate Thailand.