CHASE Manhattan is to close its retail banking business in Singapore by the end of the year, to focus on wholesale banking. ''We will now concentrate on corporate banking, private banking, treasury and risk management, capital markets and information service products in which we have strengths,'' said Michael Barrett, vice-president and senior Chase officer for Singapore. The bank's Hong Kong spokesman said the territory's operation would not change from its dual emphasis on retail and wholesale banking. ''Hong Kong is a much bigger market, especially with China at the back. However, Singapore is a highly regulated environment and foreign banks find it difficult to compete,'' he said. The bank sold its credit card business in July to Overseas Union Bank. After its withdrawal from the retail sector, the bank would continue to use Singapore as a regional support centre for its data processing, project financing and various information service products. Some staff will be redeployed to the bank's four core businesses and about 80 will be made redundant with compensation. After the closure, the bank would operate with a staff of 509 in Singapore, Mr Barrett said. The bank said its teller machines in Singapore would stop operating from December 1. Its retail business closure would affect up to 10,000 customers. Bank of America closed two of its four Singapore branches in 1986.