Actually, the leakage is right beneath my toilet bowl, so they break my toilet bowl into pieces and drilled through the cement and re-installed everything back.

The pipe seems fine, the water is coming/appearing from the cement, maybe because they didn't put any waterproofing stuff, as I recalled.

Maybe I should stop using that bathroom for a while, just to ensure there is no more water leakage then only I flooding the bathroom with water for few hours, hopefully, able to discover/prove something. What do you think?

Thanks for the advise ya!