You can fly your UA in any open field if it's more than 5km away from a civil aerodrome/military airbase or outside a protected, restricted, dangerous, or prohibited area. Use OneMap to check if your planned flying location is within these areas.

Without approval from CAAS, flying of UA is strictly not allowed within 5km of a civil aerodrome/military airbase (including open fields) or in a restricted or dangerous area.

Land management authorities may also impose additional restrictions. Look for instructional signs from land management authorities at your intended location and follow the instructions.

Please refer to the website here for more details on the CAAS regulatory requirements.