Dear Somboon-san,
First of all, we apologize for any inconvenience caused.
Kindly let me explain a bit. In any international MPLS network services, local loop from provider's (Singtel's in this case) PE router to CE router is under responsibility of LSP. Since LSP's scope is Layer 2 and below, they do not monitor Layer 3 such as packet loss and routing. It is Singtel's responsibility and they are doing so at PE router and CE router.
During the said period, TTNI-A observed packet drop and Singtel observed BGP flap, but the issue was gone in a few minutes and the link is now working fine. I am pretty sure LSP can investigate and isolate the problem and location while the issue is ongoing, however, technically it is very difficult for LSP to trace back after it's been normalized what happened in a transient phenomenon, especially in lower network layers. That is why we are suggesting loop test to try to find an issue in the link if any.
I have heard that you are coming to Singapore next week. We may propose to have a meeting with Singtel during your visit. Kindly let me arrange if you can afford time for it.
We fully understand your concern of longer restoration time of TGN circuits than before, of which TTNI is already aware. We are now discussing with Singtel how we can shorten the restoration time.