Singapore has no general statutory rent control, so a room tenancy lives largely under common law and the four corners of your contract. What you do not write down, you cannot later enforce. That makes precise drafting the whole game. Two statutory layers sit on top of the contract and you cannot draft around either.
The first is the Stamp Duties Act 1929. Any tenancy agreement, including one for a single room, is dutiable, and lease duty runs at 0.4% of the average annual rent for terms of four years or less. The duty must be paid to the Inland Revenue Authority of Singapore through e-Stamping within 14 days of signing if the agreement is executed in Singapore, or within 30 days if signed overseas. Where the average annual rent is 1,000 dollars or below, no duty is payable, which exempts many modest room lets, though e-stamping still carries evidential value. The sting is in the consequence: an unstamped tenancy is not admissible in evidence until the duty and any penalty are paid, so a deposit dispute brought on an unstamped contract goes nowhere until you stamp it. By convention the tenant pays, but both parties are jointly liable, so the agreement should say expressly who bears it.
The second layer applies to HDB flats and flows from the Housing and Development Act 1959. Renting out bedrooms requires HDB's approval before the tenancy starts, the owner must continue to live in the flat throughout, and the arrangement is subject to occupancy caps and tenant-eligibility conditions. You can read HDB's own conditions in the official HDB guide to renting out a flat or bedroom. A practical drafting move follows from this: make the agreement expressly conditional on HDB approval, so that if approval is refused the contract falls away cleanly. Owners letting a room often pair the tenancy with a clear set of personal and family documents such as a statutory declaration of occupancy where a managing agent asks for one.