I'm not familiar with the area myself but had a bit of a scout and hope this info is of use:
Designated points in both sanctuaries, listed here
, are open to visitors.
Access anywhere else in the parks or staying overnight requires permission, obtained by writing at least 15 days in advance to the Director of the Wildlife Conservation Office at the National Park, Wildlife and Plant Conservation Department, Bangkhen, Bangkok or Tel. 0 2561 4292-3 ext. 765.
I take it from that you are off to Thailand. Hope you have fun; it is really well set up for travellers, not just in the backpacker enclaves in Bangkok.
Would recommend heading up to Chiang-Mai, that was my favourite place, especially the surprisingly hip Nimmanhaemin area to the North West of the old city.
And the Khao-soi was delicious, if you hunt there is a veggie option to.