PRIME Minister Hun Sen had left Cambodia for Singapore, where his father Hun Neang is receiving medical treatment, government spokesman Khieu Kanharith said. The premier had been scheduled to open a climate-change conference at the Peace Palace on Monday but was absent. No further details have been revealed about the premier’s trip. Hun Neang, 90, received the title Neak Oknha Moha Peakdei Saporisphok-keathipadei from King Norodom Sihamoni on September 7.