I prefer Mekong, as it pours easily into the glass, whereas my Samsung will not fit. Camcorders are also difficult to get down in one. Sang Som, on the other hand pours into a glass perfectly and as Dr Dave suggests will blind you just as effectively as Mekong.
I think the ultimate drink for getting 'blind' drunk in Thailand just has to be the legendary 'See-Sip' lao khao. That stuff is evil and the Thais drink it like beer when they get up in the morning!

For those who like to live dangerously (including lorry, taxi and bus drivers), it makes a great cocktail when mixed with M-Sport and yah bah!
Olmate, you just have to try See-Sip (means '40' referring to the strength of the drink i.e. 40 degrees) to realise how vile and potent it is!