Courtesy of Marina Bay SandsTan Hong Kai, 24, from Singapore, is a senior butler at Marina Bay Sands in Singapore.Kai looks after guests in the hotel's most luxurious suites, some of which are invite-only.He said he enjoys interacting with famous guests, but last-minute requests can be stressful.This as-told-to essay is based on a conversation with Tan Hong Kai, senior butler for Marina Bay Sands Hotel.