Far more than just a side trip from the beaches of southern Thailand, the magnificent wilds and majestic mountain lake of Khao Sok National Park are one of Asia's premier natural wonders. Khao Sok stretches over some 646 square kms and is part of a greater protected area that also includes Kaeng Krung and Phang Nga national parks and Khlong Nakha and Khlong Saen wildlife sanctuaries. Spanning over 4,000 square km between them, this is a massive protected area in Thailand, and on a map it looks like an entire province of nothing but lakes, rivers, and jungle. If you're going to visit only one national park in Thailand, Khao Sok is arguably your best choice.