eVIPs work only on AA airplanes, so BOS-LHR, and DFW-NRT are both possibilities for that, assuming you have eVIPs and inventory opens up.
There is no way to use any AA currency--miles, eVIPs, stickers--to upgrade from economy to a premium cabin on another airline's airplane. The only way to use miles to get into a premium cabin for your entire trip to Thailand would be to book an award into one.
Good luck!