Have got aircon in my apartment room however since I have moved in it makes a loud sound once on.

I understand of course that some level of noise is normal but it is becoming excessive.

Any advice on what I can do to resolve this? Have attempted to speak with the reception staff but there English is about as good as my Thai; not great.

Many thanks for any advice.

Air con fan noisy, right? No problem if 1. you have money, 2. see 1.

Is it a built in unit or a more modern 2 piece system....i.e a compressor outside with the fan unit/cooling vanes inside (Split unit)?

Split units are easier to work on and sometimes the spinning cylindrical fans just need a good clean...or perhaps a vane/fin has become bent. Easy fix....but if a bearing has gone then that's another kettle of fish.

Speak to other falangs in your unit black and ask whom they use for repairs.

Lower the speed? Often that is all that is required. If not then service is in order and bearings are easy enough for them to replace (if needed and available).