SHD height - EPSG:6916

WKT

VERTCS["SHD_height", 
	VDATUM["Singapore_Height_Datum"], 
	PARAMETER["Vertical_Shift", 0.0], 
	PARAMETER["Direction", 1.0], 
	UNIT["Meter", 1.0]]

WKT2

VERTCRS["SHD_height", 
	VDATUM["Singapore_Height_Datum"], 
	CS[vertical, 1], 
	AXIS["Gravity-related height (H)", up, 
		LENGTHUNIT["Meter", 1.0]], 
	ID["EPSG", "6916"]]

Data from @esri/proj-codes

{
  "wkid": 6916,
  "latestWkid": 6916,
  "macro": "PE_VCS_SHD_HT",
  "name": "SHD_height",
  "wkt": "VERTCS[\"SHD_height\",VDATUM[\"Singapore_Height_Datum\"],PARAMETER[\"Vertical_Shift\",0.0],PARAMETER[\"Direction\",1.0],UNIT[\"Meter\",1.0]]",
  "wkt2": "VERTCRS[\"SHD_height\",VDATUM[\"Singapore_Height_Datum\"],CS[vertical,1],AXIS[\"Gravity-related height (H)\",up,LENGTHUNIT[\"Meter\",1.0]],ID[\"EPSG\",\"6916\"]]",
  "description": "SHD height",
  "authority": "EPSG",
  "version": "8.5.1(10.3.1)",
  "deprecated": "no",
  "areaname": "Singapore",
  "extent": {
    "slat": 1.13,
    "nlat": 1.47,
    "llon": 103.59,
    "rlon": 104.07
  }
}