Single 91x190cm or Super Single 107x190cm sizes fit HDB common bedrooms well enough. Leave ~60cm clearance on the exit side for easy movement. A 12 sqm HDB common bedroom typically accommodates these dimensions without crowding issues. Standard length 190cm doesn't vary for all sizes for consistency and planning very easily.
Solid wood and plywood frames outlast particleboard frames in humid conditions significantly. Rubberwood is a common affordable hardwood option for children's beds. Untreated leather can grow mould without wiping and ventilation in Singapore's 80%+ humidity. Foam density drives how long cushions hold shape over time effectively.
HDB lift door opening is the real limit at 90cm wide usually. Standard HDB door measures 91.5x213cm but corridors often restrict wider items. Leave a 2–5cm buffer to get the frame through the lift door. Internal doorway limits usually don't dictate what enters the room safely and easily.