A MAN released from prison last year was yesterday jailed for 15 months for his role in a triad gang attack. Sentencing Ngan Kam-wah, 21, in the District Court, Judge Whaley said that although Ngan had learned from his experience in prison, a custodial sentence was inevitable because such attacks were intolerable. Ngan had taken part in the attack after he was beaten up by a gang in Nam Tin Estate a few days earlier. He was questioned in triad terminology during the assault as to ''where he belonged'', the District Court heard. After the beating, Ngan sought help from a triad ''big brother'' Ah Keung. Ngan recounted the assault to Ah Keung and sought his help to get even with the gang, the court heard. On July 15, 1992, Ah Keung and two of Ngan's triad ''brothers'' went armed to Nam Tin Estate looking for Ngan's assailants, the court heard. During the attack, Ngan stabbed Wong King-man in the back, inflicting multiple injuries. He was arrested on August 19. Ngan was convicted after trial of wounding with intent and a probation report was prepared for yesterday's sentencing. The court heard Ngan had committed burglary five months before the wounding offence and had been sentenced to 12 months. imprisonment last February. He was released in October.