I would like to confirm the IP that the Local ISP is testing in, is it 118.175.33.37?
This IP also belongs to your local ISP, TOT, and you could ask them to check whether this IP is accessible or pingable. Please provide a ping test from your equipment as a prove.
Furthermore, this is not the 1st time the service is down but the local ISP informed that everything is ok but during site visit is when the engineer detects the modem was faulty.
I would really appreciate if your team could assign an engineer to site to confirm on the modem status.
Please get back to us as soon as possible as this has been pending for a long period and we would like to close this issue as soon as we can.