There are no direct buses from the THV to the parks. You'll have to take a shuttle bus to SSR, and transfer to a park bus there.
The shuttle bus runs about every 15 minutes, and the park buses are supposed to run at least every 20 minutes, but occasionally there may be a longer wait.
There are 2 shuttle bus stops in the THV. It looks like the longest walk from any villa would be about 1/8 mile.
There is a walkway from the southeast corner of the THV to the Grandstand section of SSR. From the closest villas, it's a 5-10 minute walk to the Grandstand bus stop, which would let you avoid the extra wait for the shuttle bus.