In 2002, the Philippine National Team,were formed for the Asian Games in Busan. He made his debut during a 2002 PBA Governor's Cup game for the Selecta RP Team, one of two RP Pool team that played in the said conference.
Alapag played for Team Pilipinas in the 2005 FIBA-Asia Champions Cup and the 2005 Brunei Cup when they won the title. In 2006, he played during the exhibition game against the Dennis Rodman-led US team and against the Lebanon national team. And in 2007, he once again played for the national team that competed in the Olympic-qualifier FIBA Asia Championship 2007 and was the team's spiritual leader. The following are some of his contributions to the 2007 RP Team:
lead team in scoring with 16.0 per game (9th in the tournament)
lead team in assists with 2.8 per game (6th in the tournament)
lead team in 3PT-FG% with 42.49% in 12 of 28 shooting (11th in the tournament)
man rensponsible for the top 2 best scoring performance in a game by any player in the team, scoring 32 points vs Syria (10th in the tournament) and scoring 25 vs China (24th in the tournament).
In 2009, the Philippines was preparing for the 2009 FIBA Asia Championship. The team's target was to finish 3rd place or better in order to automatically qualify for the 2010 FIBA World Championship. However, Yeng Guiao, the team's new head coach, did not include Alapag in the line-up. Olsen Racela, a 2-time member of the Philippine National Team, said coach Guiao should include Alapag in the team.