Anyone from Penang island here? I'm from Bayan Lepas area, staying in high rise with centralized antenna. I can receive  ch45 (tv3, ntv7, 8tv, cjwow etc) but not rtm channel. The signal strength for ch45 is 100% and quality from 70%-90%, but all other ch signal strength always 0%. Not sure what is the problem

Mean that your antenna is VHF, not UHF antenna.
Either fine tune you antenna direction/position or get Cheap Thailand 5e antenna (lazada or Shopee ~$30/=)should be able to resolve it.

Inform the building management about this.. The centralise antenna may need to do some realignment by the technicians.

Or else, contact MYTV and tell them about this.

My nephew double storey landed house use thai 5e at Bukit Tengah(install at 2nd floor outdoor, bought ~$30/=), install with correct direction and position work great (above 90% signal Quality)! Don't buy those cheap below $10/= antenna, get those Digital antenna with Amplifier, it should work better if the Management can't help you resolve centralize antenna. and you need to enable Antenna Amplifier to ON, through software setting (either TV box or TV own setting).

honestly i would rather use the 5e antenna indoors than those so called "120km indoor antenna" 

me in the gang.