@Highball is spot on with the home made video approach.
Best ways to learn a language is Saturation Technique and Cognitive Recognition(CR).
So for Saturation, include things like listening to English radio and watching the news, suggest something like Tim Newton Today (TNT) as only 10+ minutes daily, so if she watches Thai TV news bulletin then ties in with CR. When crash coursing a language for business, then living in the actual country is highly beneficial. (Not applicable in your case). Also watching Thai movies with English Subtitles.
As a teenager learning French use to read Tintin, Lucky Luke and Astérix comics in French, so not just the basic "La plume de ma tante" you get in French text books. Improves vocabulary and also gives you a more conversational approach.
For basic steps, start with numbers before alphabet, easy to relate to as Thai's use the same Arabic numbering system. Also she needs a basic Thai-English pocket sized dictionary.
Another top-tip is fridge magnets letters or a white/black or cork board. Useful for leaving simple instructions which she can confirm back on.
There use to be a book and course ( video) called English in 750 words, not sure if still exists, but was a big success in the London based language schools in the 80's / 90's.