Teck Yong, head of fx cash and derivatives sales at Royal Bank of Scotland in Singapore, has resigned. Traders believe Yong will take a month off before resurfacing at another firm in the Lion City. At RBS Yong reported to Simon Chan, head of fx in Singapore. Chan was traveling and could not be reached for comment. Yong could not be reached. An RBS currency trader said the firm plans to hire a replacement for Yong.