Kathoey in the Thai language refers to trangendered men. The term is not used for women who dress and act as men; they are called tom, from the English word tomboy. My impression is that kathoey are more likely than tom to have their genitals surgically altered to resemble those of the opposite sex.

In Thailand kathoey are popularly thought of as inverts: they have a woman’s heart in a man’s body. The term for heart in Thai - jai - is freighted with significance, and people speak of differences in character, comportment, and behaviour as arising from – indeed, determined by - the heart. Kathoey, then, are biological men who rework their appearance to perform the role of their gendered hearts, not their anatomy, suggesting that hearts are more important than genitalia in structuring gender identification. Indeed, the popular view suggests that for Thai kathoey are not gender-crossers at all, but people whose gender doesn't "match" their biology. The Thai language recognizes biological sex in distinguishing phuying, people with vaginas, from phuchai, people with penises, but popular conceptions accord people gendered hearts as well. Though dominant norms of gender performance are recognizable to farang - westerners - and rest on the twin poles of gender familiar in the west – masculine and femininesecondary but highly visible alternatives suggest that non-genital gender constructions are equally possible in Thailand.

Thai, like farang, usually assume that sexual object choice will reproduce dominant heterosexual norms: those gendered masculine will choose those gendered feminine as partners, and vice versa. Many Thai I met seemed confused about homosexuality: they knew it existed, but when we talked about it, they tended to shake their heads in amused perplexity and ask what exactly two people do in bed together - the proclivity to equate sex with heterosexual penetrative intercourse being common in Thailand and the west. The general assumption, then, is that kathoey are penetrated by their (presumably male) lovers during sex.

Gay Australian sociologist Peter Jackson has written extensively and intelligently about male homosexuality in Thailand, and he confirms this assumption. He contends that the salient opposition in Thai constructions of masculinity is kathoey versus “man” - the inverted commas signifying for him the sex/gender category phuchai, not the biological category male. Kathoey and “man” are “polar opposites, nuclei for two constellations of sexual norms and gender characteristics regarded as being mutually exclusive and as constituting a male's sex/gender identity”. “Man” is a valorized category, kathoey vilified. Jackson refers to kathoey as “the negation of manhood...the Thai 'un-man'”, and attributes to them a pivotal role in the construction of masculinity: a male knows he is a “man” because he is not a kathoey. Kathoey are not like “men” in “dress, speech, or demeanor”; unlike “men” (and like “women”, phuying), they occupy the subordinate (penetrated) role in sex acts; they do not marry and father children.

One way that Jackson analyzed this was to look at magazine columns by “the 'Dear Abby' of problem-hounded Thai homosexual men and women”, Go Paknam. Paknam distinguishes males who penetrated other males from those who were penetrated. In modern Thai slang, the penetrators are known as gay king - another English borrowing. Paknam viewed gay king as “true men”. The men they penetrated, gay queen in slang, passive homosexuals in Jackson's parlance, were largely assimilated by Paknam into the category of kathoey: he assumed gay queen likely, and kathoey always, to be effeminate and receptive in homosexual acts. Paknam viewed gay king as “wayward heterosexuals” and advised them to use “concerted effort” to force themselves to conform to dominant sexual norms; by contrast, he considered tom, gay queen, and especially kathoey unable to escape their sorry fate.

Jackson perceives that in the indigenous Thai sex/gender system, “private sexual practice” is “largely ignored” and “evades cultural and legal sanction”, though public proclamation of sexual preference is “regarded as highly inappropriate”. The kathoey is impugned for publicly breaching gender norms, but the homosexual who keeps his sexual infractions private is tolerated. The newly emergent category of gayness presents a radical challenge to this indigenous sex/gender system “by making public what was previously private and by seeking general approval for the conferral of masculine status upon exclusive male homosexuality”. Gayness brings into the open “an overlooked 'little tradition' of masculine homosexuality”, “renders explicit what was previously implicit, and transforms into an identity what was previously a behavior”.

Though in Jackson’s view this is not a radical transformation, I disagree with him here. As Foucault has argued so convincingly, subjectivization which calls for the subject to both look inward to define the self and turn outward publicly proclaim that truth is intimately tied up with regimes of discipline which in the west have seen institutions like the state and medical and psychiatric professions gain power to scrutinize and punish individuals for deviations and infractions. And indeed, in Thailand, kathoey and their ilk are increasingly subject to disapprobation and discipline.

Peter Jackson’s work, which I have quoted from above, includes his article "Kathoey - Gay - Man: The Historical Emergence of Gay Male Identity in Thailand" in Sites of Desire, Economies of Pleasure: Sexualities in Asia and the Pacific, edited by L. Manderson and M. Jolly, and his book Male Homosexuality in Thailand: An Interpretation of Contemporary Thai Sources. His novel, The Intrinsic Quality of Skin covers many of these same themes in what some may find a more accessible fashion. See my writeup on tom for different, but equally interesing, information on the female counterpart to kathoey.
