The 23-year-old Boonjumnong was as galloping stallion to the old, tired beaten warhorse that was Brin.
Learning bitter lesson from their past encounter, the Thai waged a disciplined fight, repeatedly beating the Filipino veteran to the punch and dancing away after close exchanges to post a decisive 29-15 victory at the Peristeri boxing hall here.
With the 32-year-old fighter bowing out of the Games after serving the country in 1996 in Atlanta and four years ago in Sydney, only light flyweight Harry Tañamor is left in the fast dwindling ranks of the 16-man RP contingent.
And Tañamor faces another acid test in his division when he fights Hong Moo Won, an experienced Korean who made an impressive debut Saturday night. Tañamor beat Tajikistan’s Sherali Dostiev in a close contest earlier.
"Naunahan ako sa diskarte, tapos tinakbuhan," said Brin, plucked out of semi-retirement to emerge an eleventh hour entry in the Asian qualifier in Palawan last January.
"I am very proud to beat Brin as I lost to him in January. While I was boxing I was thinking of my King and my parents," said Boonjumnong who will now face the tough Willy Blain of France. The French slugger whipped the Russian Tank, Alexander Maletin.
Brin was completely outfought and outclassed in four rounds, evidently beaten to the draw and his corner simply outwitted by the brilliant Cuban coach from the Thai camp.
"We learned a lot the last time, my coach said we wouldn’t use the same technique. This time we wait for the Filipino to come in and box, box and move away," said Boonjumnong.
And he followed the battle plan crafted by Cuban coach Juan Batista Fontanills who was chiefly responsible for the two golds Thai boxers have won the past two Olympics.
The 5-foot-7 Boonjumnong, bronze medallist in the 2003 World championship in Bangkok, fired away right hand leads and immediately set the theme of the fight as he took a 5-2 edge in the first round.
Brin charged out of his corner, put the pressures on by chasing the Thai with stinging lefts and combinations to score three blows at 5-7, but Boonjumnong went back to his stick and move tack and countered with rights to regain momentum at 15-7 at the end of the round.
The Thai completely dominated the Filipino fighter in the third round, limiting Brin to single left cross while firing away with clean shots with relative ease for a 22-8 count.
Boonjumnong then moved on to a crucial quarterfinal date with Blain by riding out a last ditch attack by Brin in the final round for 29-15 count. He became one of five Thai boxers who have so far survived the cut-throat elims, the only casualty being former Olympic gold medallist Somluck Kamsing.
The reigning world champion Blain outlasted Maletin by extending a five-point lead in the third round to eight at the finish, 28-20.
Thus ended Brin’s saga in the Olympics that began in the Atlanta Games eight years ago and took an incredible twist with his amazing comeback from semi-retirement to sweep the opposition, including Boonjumnong, in the Asian qualifier in Palawan last January.
"Hindi para sa atin" said Brin, one of only 11 Filipino athletes who have donned the national colors in at least three Olympics since 1924 in Paris.
His ouster and swimmer Miguel Mendoza’s completion of his stint in the 1,500-m freestyle at the Aquatic Center, now left only Tañamor, taekwondo jins Donald Geisler, Tshomlee Go and Maria Antoinette Rivera and tracksters Eduardo Buenavista and Lerma Gabito in the fast dwindling RP ranks in the Games.
The 22-year-old Mendoza, the Hanoi Southeast Asian Games gold medallist, failed to improve his qualifying time and national mark of 15:49.55 when he checked in with 16:26.52 in the second heat in the preliminaries. He wound up 34th and last in the event he considered his favorite. He had earlier swam in the 400-m freestyle event.
"We should not lose heart. We must keep on fighting until the last man," said Philippine Olympic Committee chief Celso Dayrit.