How to play 2-player mahjong (Siamese)
Two people can play American mahjong with the Siamese variation. Each player sits behind two racks and builds two 14-tile hands at once, one per rack, both matching the card. East takes 28 tiles, the other player 27, there is no Charleston, and the game ends when one player has finished both hands.
Setup
Each player uses two racks, facing the other player. Build the walls as usual, or for a casual game leave the tiles face down in a pile in the middle and draw from it.
The deal and play
East takes 28 tiles and the other player 27. There is no Charleston. East discards first, then you take turns: pick a tile, discard a tile.
Two hands at once
You build a separate 14-tile hand on each rack, and each must match a hand on the card. Declare mahjong and lay out a hand as soon as it's finished; the game ends when a player completes both.
Jokers
You may swap for a joker in your own exposures or your opponent's, but never from a hand that has already been declared mahjong.
Scoring
Your first hand scores its card value; your second hand scores double. The player behind pays the difference.