A proposed dam that would flood part of a national park in western Thailand represents a "significant new threat" to the kingdom's tigers, wildlife group WWF warned on Wednesday.

It said the success of conservation efforts in the area near the border with Myanmar -- highlighted by new video footage of a tigress and her two cubs filmed by camera traps close to the proposed dam site -- were now at risk.

"As tigers need large amounts of food, especially when they are nursing their young, the new footage indicates that prey in the Mae Wong-Klong Lan forests is abundant enough to support tiger reproduction and recovery," said WWF conservationist Rungnapa Phoonjampa.

Many tiger prey species including wild pig and deer were also seen in the area, according to the group.

"Years of successful conservation efforts will be washed away if the dam construction goes ahead," said Rungnapa. "The Mae Wong dam must be stopped or we risk losing our tigers."

Fewer than 300 tigers remain in the wild in Thailand while around the region the Indochinese tiger is under threat from shrinking habitat, illegal trade in tiger parts for traditional medicines and a scarcity of prey, WWF said.

The multi-million dollar dam project would destroy more than 20 square kilometres (7.7 square miles) of national park home to sambar deer, an important prey species for tigers, the group warned.