梭发那·富马亲王
On 18 April 1964 there was a tripartite meeting on the Plain of Jars, as Souvanna Phouma met with his brother Souphanouvong to thrash out a coalition agreement. At this meeting, the Pathet Lao demanded the demilitarization of both Luang Prabang and Vientiane. A discouraged Souvanna Phouma returned to Vientiane, having decided to resign as Prime Minister. However, King Sisavang Vatthana would not approve the resignation until the following day.