Anyway, I always assumed "me love you long time" was the best translation of something along the lines of "I have admired you from afar for some time now" you could manage with little knowledge of English grammar but access to a dictionary. Except no-one's said anything even half that stupid since 1827. Not even me.
So I have wikipedia to thank, via a friend's comments on Thai-Burmese relations, for an article on Prositution in Thailand which has a far more plausible explanation:
sexual services ... generally divided into "short time" (at most a few hours) or "long time" (overnight).
So something like "my services are available for the duration of the night" is probably closer to the phrase's meaning, though that does seem very prosaic in comparison and unlikely to catch on.