This is more of a problem with somewhat less educated Singaporeans, although the StR has a lot of staff from the Phillippines (compared to Raffles, which is proud of their Maylasian staff). English is the/an official language, although Singaporeans of Chinese ethnicity are expected to learn Chinese in school too. I would expect the butlers to speak English very week and I've never had problems with this among the butlers, although I did once have an issue with the hostess at the casual restaurant by the pool and the supposed explanation was that she didn't understand (simple clear) English.