Since yesterday morning connections through any ports except standard web (80, 443) are useless with massive packet loss. This include SSH, and high ports. It's of course useless to report it to their helpdesk as for them either you can use the web or you can't, they have no idea what I'm talking about. I setup a proxy server through port 443 and using that everything is fine.

Is this problem limited to TT&T or does TOT and/or CAT have the same problem?

Actually, my TOT connection from Nonthaburi seems to have cleaned up its act a bit... ping times to North America destinations have dropped from 600ms+ to around 380ms and my ssh connections seem OK (on standard and unusual port numbers). This is following the many hours outage that TOT users seemed to suffer all over Thailand on Sunday evening.

Not to say there isn't congestion and loss, but it seems reasonable interactivity for low bandwidth TCP connections at least...

Due to packet shaping, perhaps?

I finally got a call back from a technician. He did "something" and now it works again.