On 22 December 2014 two experienced Russian technical divers got into trouble at Tiger Cave, in the Ratchaprapha Reservoir. Dmitry Dokuchave (46) died at the scene and Alexander Solomatin died later in hospital.

Tiger Cave is in the northern part of the reservoir, which is in the Khao Sok National Park. The cave was found in April 2014 and has been explored for over 500 m at depths of up to 70 m. A north-easterly trending passage is heading towards a small, isolated lake surrounded by karst hills, 800 m from the main lake. This is probably the rumoured cave where, before the dam was built in 1982, monks passed through a cave under the mountains.

http://www.nationmultimedia.com/national/Mystery-surrounds-deaths-of-Rus...

In October 2007 eight people were drowned by a flash flood in a cave in the southern part of Khao Sok National Park.
http://www.thailandcaves.shepton.org.uk/node/29