sentences:  Trade and relations between Japan and Ayutthaya were quite friendly and strong for roughly sixty years, until a series of political scandals in 1630 led to the shogunate formally severing ties with the kingdom.Following the death of King Songtham, the throne was seized by Prasat Thong in a violent coup.As part of this scheme, Prasat Thong arranged for the head of the "Nihonmachi", Yamada Nagamasa, who also served in prominent roles in court and as head of a contingent of royal Japanese bodyguards, to be killed.