Because we only have a couple a days after our tour threw Isaan/Laos for relaxation I prefer not to go to the southern Islands. (last year we went to Koh Phangang and years ago to Phi Phi also in july, it's great their but we also had pretty much rain)
So, this year i prefer to stay a bit closer to BKK and find a real pretty and unspoiled bounty beach. But offcourse I don't want the risk of (to) much stromy/rainy weather. So, where to go??? Is Chang, or Mak or... a bad choice then? Another option is flying from Udon Thani to Phuket . But honestly Phuket doesn't attract to be (to bussy, to big, nonauthentic, i loved pretty Bottle Beach on Phangan last year, and looking for something familiar). PLease tips; we'are leaving in two weeks already
July is the second wettest month of the year on Ko Chang . that means it will be absolutely pegging it down! You may get some good weather, but you'd need to be lucky.
That time of year, close to Bangkok, I'd recommend Ko Samet -- it is drier, even in wet season.