I couldn't do it either in the App so just sent a pic to the hotel but got no reply but its in my sent items if asked on Day 5. I've just been back into the app again and in the notifications there is now a link to upload a photo so I've uploaded and it's worked so now I m 'low risk'.
Just keep checking the App I'd say as may mysteriously appear as mine has!!
okay thanks Simon, I'm going through Rayong next week on way to Koh Chang so will have a Google and see if can locate some assistance in Pattya as there for 2 days π