
Qinghai Province (Zaqu is located at the south of Qinghai)
A view of Mekong River at at Luang Prabang , a city located in north central Laos
Source: http://en.wikipedia.org/wiki/Mekong_River and http://en.wikipedia.org/wiki/Luang_Prabang

A view of Southern Laos from the Mekong River
Source: http://en.wikipedia.org/wiki/Mekong_River

A tourist travelling along the Ruak River
Source: http://farm3.static.flickr.com/2173/2130030692_cd9a65bf78.jpg

A view of the Golden Triangle
Source: http://en.wikipedia.org/wiki/Mekong_River
The river then divides Laos and Thailand, before a stretch passing through Laos alone. It is known as Maè Nam Khong (Mother of all rivers) in both Lao and Thai. The river again marks the Lao-Thai border in the stretch which passes Vientiane, followed by a short stretch through Laos alone.
A view of Mekong River in Vientiane
Source: http://i.pbase.com/u35/andrewd/upload/23391803.IMG_1552.jpg
In Cambodia, the river is called the Mékôngk or Tonle Thom (great river). Just above Phnom Penh is the confluence with the Tonle Sap, the main Cambodian tributary. Below Phnom Penh, it divides into the Bassac and the Mekong proper, which both flow into the Mekong Delta in Vietnam.

A view of Mekong River from Phnom Penh
Source: http://andybrouwer.co.uk/200311.jpg
In Vietnamese, the river as a whole is known as Mê Kông. The part flowing through Vietnam, known as Sông Cửu Long (river of nine dragons), divides into two major branches, the Tiền Giang (Front River) and Hậu Giang (Back River). These in turn enter the sea through nine estuaries, thus the Vietnamese name. Here are the pictures for the tributaries and distributaries of the Mekong River.
A detailed picture of the tributaries of Mekong River

There are 5 distributaries for Mekong River: Bassac River, My Tho River, Ham Luong River, Co Chien River and Ba Lai rivers. The above picture is the Bassac River.
Source: http://en.wikipedia.org/wiki/Bassac_River