In my country I never take my mac to certified Apple repair shop any more. Last time they said the logic board was dead and wanted me to spend 900EUR to replace it. I took it to another laptop repair shop where they replaced a cap on the logic board and my MBP is running well two years since. I saved 800EUR.
I can understand that replacing Logic board is safe way to handle the problem. We do not know what else may have been killed on the board. But if you are willing to take a risk spending a little you may get lucky.
So take your MBP to your local laptop repair that can repair mac's and see if they offer you a different solution.
But as what may have killed your mac you never know. I bought a iMac second hand. When I picked it up it was working fine. At home it did not turn on. Between shut down and start up the power unit died. These days where mac was built to work for many years have gone with Pismo and Quicksilver.

Yes, there is a place I could try in BKK, but I'd have to find it first.

Maybe ThreeBKK could refresh my memory of where it is? Around Din Daeng, was it?