Not much is know about the Tongs, they are mentioned multiple times through the events of Chinatown Wars, but they never make a physical appearance. They appear to be a council or a very important gang, as representatives of each gangs within the Triads, mention that the Tongs have a great influence on the choosing of the new Triad boss in Liberty City.
Events of Grand Theft Auto: Chinatown Wars
Later in the game, in Raw Deal, Chan was about to make a drug deal with the Spanish Lords, to broker peace between them and the Triads in an attempt to impress the Tongs, but he was deceived, and ambushed by the Spanish Lords.
Later, Kenny Lee then gave Hsin the files refering to both Zhou and Chan as the rats, and Wu being named as the new boss sent Huang to kill them (Hit from the Tong and Clear the Pier). After Huang eliminates them both, it turns out that Kenny was the real rat.