On the scales the Thai was 154lbs dead on the limit and some 36lbs heavier than he was during his first world title reign back in the mid 1990's. Nazareno on the other hand was reported as being both 153.5lbs and 154lbs according to differing sources, though it is clear that he also made weight for the contest.
Coming into the bout the Filipino is 1-5 in Thailand. His sole win was his debut in the country and saw him defeating Manfa Luksaikongdin back in Septemeber 2010. Since that win he has lost to the likes of Prawet Singwancha, Teerachai Kratingdaenggym, Chalermpol Singwancha and of course Sirimongkol. Notably however he has never been stopped in Thailand and in fact hasn't been stopped since he was taken out by Min Wook Kim in an OPBF title bout back in November 2012.
Amazingly Sirimongkol hasn't lost since August 2003, when he was out pointed in the US by Jesus Chavez. Since then he has run up a 40 fight winning streak, one of the longest in the sport, and spent time in jail. He is however 38 now and it would seem that father time will defeat him sooner or later, especially given his long career which began way back in 1994.