If you like a break to stretch your legs and breath normal air, then Oman is a good option. I've done their route twice and it's have no qualms booking them again.
If you prefer to do the long haul and get it over with, I'd say EVA is definitely the better option at the moment
Bangkok Bank aren't very good at this stuff, I'd go back again and explain that the card isn't working for any websites outside of Thailand. I had the very same problem with Bangkok Bank and it turned out they had activated for online transactions but not for transactions outside of Thailand. After insisting they needed to recheck everything several times, the guy on the phone eventually admitted that they hadn't set it correctly and resolved the issue for me.
it's also worth considering that just because a school is "international", it doesn't mean it is offering a high quality of education. You should really do your homework on any school you consider if you value your child's education. Don't accept exam grades and stats as evidence of performance because schools create their own exams and are responsible for their own scoring and grading.