5 willing ladies.
1 Lady-boy (It's important that the lady-boy looks just as attractive as the 5 ladies to the uninformed observer).
2, 3 or 6 heterosexual male players (if using a different number of players, adjust the required number of ladies accordingly).
Any number of "non-players" to round up the necessary lady-boy and ladies; the players must not be told which one the lady-boy is.
After a non-player has arranged the assortment of "ladies" in a random order, player 1 must walk up to one and perform or receive a sexual act (the act must be pre-aranged and performed by all players. It is up to the players to decide the act), followed by player 2 and so forth. Once a "lady" has been chosen by a player, they stand next to the player for the remainder of the game and are unable to be chosen by another player. After all the "ladies" have been paired up with players they start to remove their pants until the lady-boy is revealed. The player who chose the lady-boy must be ridiculed by his fellow players at every opportunity from then on for the rest of his life. Bonus points are awarded for presenting video evidence to the unlucky player's girlfriend/wife/mother/work colleagues etc.
Jim: "Great! Played Thai Roulette. Wanna see the video?"