sometimes it seems like everyone is already doing it - - great dream but you seem severely under capitalized if you want something nice. And then, who will be your 51% partner. Have you checked the price of land in the area that you think your customers might want to stay? The areas where the tourists want to be are surely very expensive already - if you want to be off the beaten path, advertising will be expensive and I don't think people go to Phuket to be out of the main action...
As a foreigner, you cannot run tours, renting out equipment that will get damaged and then fighting w/your customers does not sound like fun to me - and with people doing activities, I would guess that you will need a fair amount of insurance... it's sad but tragedies happen there often partly because people drink too much and become belligerent and violent - is that also part of your dream, fistfights, knife fights w/out of control customers?
There is not much you can create on your budget,,, it is like opening a restaurant and only having 2 tables - you might be full all night and not make any money...
If you have never run a business like this - you will need a professional to run it for you - I don't guess it will be as idyllic as it sounds... good luck to you.