SINGAPORE, June 17 (Reuters) - Singapore’s May non-oil domestic exports (NODX) expanded 8.8% from a year earlier, official data showed on Thursday, driven mainly by non-electronic shipments such as specialised machinery, petrochemicals and primary chemicals. The year-on-year export growth was below economists’ expectations in a Reuters poll for a 16% rise and compared with 6% growth in April. On a seasonally adjusted month-on-month basis, exports fell 0.1% in May, Enterprise Singapore data showed, versus the prior month’s 8.8% contraction. Economists had forecast 4.7% growth. Reporting by Chen Lin in Singapore; Editing by Jacqueline Wong Our Standards: The Thomson Reuters Trust Principles.