There is a guy in Bangkok called Chris Wright whose Dad, Bruce is a Brit and his mum is Thai. Totally bi-lingual. He used to have a TV program in Thailand teaching English but explaining in Thai. He's actually quite funny and my GF loves watching his YouTube videos giggling her way through them and she has learned quite a lot.
Here is a link to his YouTube videos.
There are dozens of them.
The GF was in Bangkok waiting for a visa a few weeks ago and I sent her to his school in the Center World shopping Mall for a few days for a few 2 hour private lessons from his dad Bruce. Lessons were £20 an hour one to one and she came back with a few very good books that have helped me teach her quite a bit. The most expensive was 1000 baht but it is an A4 pretty thick book. He was specifically briefed to work on her pronunciation and he did quite a good job but the two of us try and spend an hourish each day where I correct her when she gets things wrong in generak conversation. Much more than that and she would go mad.
Not sure they will send the books out by post but if you Google the Chris Wright school in Bangkok you can check. I was pleasantly surprised to hear a Thai guy answer the phone when I rang the school with very good English.
The GF was taught Tinglish at the hotel where she used to work so there is quite a bit to undo where she was originally taught by Thai English teachers who simply couldn’t speak English well themselves.