Upgrade the enterprise server machine to 11.5 or later. Starting 11.5, by ref map and feature services use industry standard IANA time zone library while converting date/time value to UTC epoch as is required by the REST specifications. Using of standard time zone library resolves time zone conversion of historic data.
While publishing from ArcGIS Pro, use version 3.5 or above and pick "(GMT+08:00) Singapore Time (Singapore Standard Time)" from IANA time zone list on the Sharing pane or on the layer's Properties page.