Booking used to go pretty smoothly for me, then a year or two ago they changed to some local Thai bank for the payment portion of the booking. I don't recall off hand which Thai bank it is...maybe Kasikorn or SCB. Anyways, when they made that change I have the occasional failure in booking. Usually due to a timeout in the bank processing it. It's also a pain with the Verified by Visa part because I'm using a Korean credit card, and it kicks over to my Korean bank's site for which I think 100% of Korean companies only work with IE, and not any other browsers. So I always have to switch to IE when doing any TG bookings. For those in other countries/other banks processing your verification (not the Thai bank portion), your mileage may vary. Anyways, whenever booking online with TG these days, I try to only do it when I'm sure I won't be interrupted and concentrate on doing the booking as quick as possible so I don't run into the silly minimal timeout.

TG's IT is pretty bad, but even more ridiculous is Korean IT (Asiana, KE, and any Korean business). Korea has one of the most advanced IT infrastructures, but IT software engineers and ridiculous government IT policies that are back in the dark ages. It's really totally pathetic, especially given that Korean engineers are vary capable, but they simply don't have the slightest clue about how to build a decent usable website that foreigners can use.

Then you have that total screwup that SQ did a few years back when they changed their booking engine and made online booking a nightmare at best, or more likely impossible. And rather than immediately firing the bozos that screwed it up, they kept at it, taking forever to fix the issues, while their customers suffered. I actually don't even know what the final result is as I don't book SQ flights anymore.

I was a member of BD for a while, and saw the endless complaints about their IT, which I believe was outsourced to India.

After the CO/UA merger, I had many issues with the UA site that would make all the above issues look minor. Things like auto rebooking my tickets onto invalid connections (ie. they had me departing on a connecting flight before I even arrived on my prior flight) and then never informing me of the changes.

So as bad as TG is, it actually could be worse. Incompetent IT departments are one of my biggest pet-peeves, and unfortunately in this world amateur IT engineers and managers are taking over most of the corporations. I don't necessarily blame the IT departments directly though because many times it's likely management trying to save money and wanting to cut the salaries and budgets for their IT department. If you're only willing to pay peanuts, you're going to get monkeys working for you. In Thailand, IT is relatively cheap though, so no excuse for TG not spending the effort to get it right.