Complex sentence: In his engagement as a politician, initially, he was a member of the Sam Rainsy Party, listed of as a nominee since 1998 but not elected, later in 2003 he was elected as a representative for Prey Veng Province.
Split into simpler sentences: In his engagement as a politician, initially, he was a member of the Sam Rainsy Party, listed of as a nominee since 1998 but not elected. Later, in 2003 he was elected as a representative for Prey Veng Province.