as far as i know, they are just kind of a generic kitchen/utility knife common in thailand. here are some more being used as throwing knives, meed eneb? meed maw or mawr
and here is a decorated temple version with 'magic' powers,

the site is
HERE <-linky, called a meed mor. (herb knife? - bit big for that tho) meed=knife, saw another one for sale on ebay as a meed mong, another as a thai kukri
see also post 14
HERE