Tun was elected to the Senate of Micronesian Congress from Yap district.

[4] He was instrumental in negotiating the first Compact of Free Association between the FSM and the United States and later served as the first Vice President of the Federated States of Micronesia during the first term of President Tosiwo Nakayama (1979–1983).

In addition, he held other high positions in both government and private industries.

He would later be the Chairman of the FSM Delegation that negotiated the Amended Compact of Free Association with the United States that went into effect in 2004.

After his death, the widely respected Tun was honored by a state funeral, which was attended by a large crowd including fellow Founding Fathers of the FSM, and laid to rest in his Municipality of Gagil.