Yep, leaning towards this. I'll probably advise her to try to book on a single itinerary with an extended layover in BKK (if Thailand Pass allows it). Otherwise, she'll have to book all her luggage on a separate domestic flight where the cost can rack up quickly.
If it's the same as before with the CoE, the coverage will have to last as long as your visa (so will need to cover to the expiration date in August) regardless of if you plan to extend.