Car mods which does not require LTA approval:

Bumpers

Car seats

Fog lamps

Fuel additives

Fuel molecule polarisers

Gear knobs

In-vehicle entertainment systems

In-vehicle information & communication systems

Intake air filters

Intake manifolds

Meters and gauges

Radiators

Rollover bars

Roof racks

Seat belts

Side skirts

Side windows and partitions (for light goods vehicles)

Spark plugs and spark plug cables

Spoilers

Sports rims (for cars only)

Steering wheels

Sunshades

Suspension systems

Tinted films

Tinted glass

Tyres

For more information on this, you can visit https://onemotoring.lta.gov.sg/content/onemotoring/home/owning/modification.html