Why did president nixon authorize the bombing of cambodia and laos?

Because the v.k. would use Cambodia and Laos as part of the chi Minh trail to be able to transfer guns and ammunition 

"A change in the Cambodian government allowed a window of opportunity for the destruction of the base areas in 1970 when Prince Norodom Sihanouk was deposed and replaced by pro-US General Lon Nol. The operation was also in response to North Vietnamese offensive on March 29 against the Cambodian Army that captured large parts of eastern Cambodia. Allied military operations failed to eliminate many communist troops or to capture their elusive headquarters, known as the Central Office for South Vietnam COSVN, but the haul of captured material in Cambodia prompted claims of success."