As your comments about COO., we asked with my shipping. They informed us that Thai Chamber of Commerce will issue amount of COO as per amount of B/L cannot issue just 1 set with several b/l.
Example: For Diamond Cement, you would like to split b/l in 3 sets. COO must issue 3 sets as per amount of b/l but the another related docs, we can issue just 1 set. ( Commercial invoice, all documents by SGS and manufacture certificate)