Pronunciation of –s suffix

This notice, seen in Ikea cafés in Singapore, encourages customers to clear their trays after eating.  As can be seen, in Singapore English pronunciation, trace and trays are homophones (different words pronounced identically): both are /treɪs/. 

By contrast, in other varieties of English, e.g. British, trace would be /treɪs/ and trays, /treɪz/.  The suffix –s, as a possessive (e.g. Chuck’s), plural (e.g. Chucks) or third-person singular present tense (e.g. chucks) marker, is realized as /s/ after voiceless sounds and as /z/ after voiced ones (vowels and voiced consonants).  This rule applies to trays, whose singular form, tray /treɪ/, ends in a vowel (voiced) sound, but not to trace /treɪs/, where the /s/ is not a suffix but part of the root.