is that possible i can apply vietnam visa here in thailand. ?

i just wondering if i can apply the vietnam visa here in thailand but i use philippinbes passport and i have only holiday visa here in thailand like 3 months visa. i want to apply 6 months vietnam visa... is that possible even im not in my own country? bcoz i heard that we have 21 days stamp visa in the first arrival. is that true? and or we can apply the 6 months visa in vietnam airport.? is that possible.? thank you and i hope to hear your answer asap...