MORE than 800 army cooks, post officers, drivers and engineers based in Hongkong become members of the same regiment today as six units in the garrison merge as part of the creation of the new Royal Logistic Corps (RLC). The garrison will mark the formation of what will be the British Army's largest regiment with a parade on Thursday, which will be reviewed by the Commander British Forces, Major-General John Foley. In Hongkong, the units forming the new regiment are from the Royal Corps of Transport, Royal Engineers, Composite Ordnance Depot, 50 Hongkong Workshop and the Army Catering Corps. ''The new corps' aim will be to provide logistic support to the army in peace and war. Its tasks will be wide-ranging and no other part of the army will have a greater span of responsibility,'' said a garrison spokesman. As a whole, the RLC will be made up of more than 27,000 officers and soldiers and will be 14 per cent of the British Army's overall regular manpower and 20 per cent of the army's volunteer numbers.