You can invest into STI ETF and likewise other SGX listed ETF via the local brokers.
iFast should be the cheapest currently. $10 min /0.08% commission.
Though its good to diversify beyond STI ETF.. below are the ETFs I have short-listed for my SRS portfolio. You can access to them via the same broker.
Equities
i. STI ETF (ES3) - Vested - TER: 0.30%
ii. Lion-OCBC Sec Hang Seng TECH ETF (HST) - TER: 0.68%
iii. Xtrackers MSCI China UCITS ETF (TID) - Vested - TER:0.64%
iv. SPDR S&P 500 ETF (S27) - Not vested - TER: 0.09%
REITs
i. NikkoAM Asia Ex Japan REIT ETF - Not vested - TER: 0.60%
Bonds
i. ICBC CSOP FTSE Chinese Govt Bond ETF (CYC) - Vested, TER: 0.25%
ii. iShares Asia High Yield Bond ETF (QL3) - Vested - TER: 0.50%
Gold
i. SPDR GLD ETF (O87)
bid-ask spreads for ES3, CYC, QL3 are pretty decent. around 0.10% to 0.20%.
Spreads for TID and S27 is higher at around 0.50% to 1% but since I am holding it long-term, its better than paying annual management fees to Endowus and Stashaway.
Will use the above ETFs to maintain a 70% Equities 25% Bonds+REITs portfolio and 5% into Gold.
Within Equities, 30% Singapore, 30% US, 40% China.