The Filipino booters were holding their own against the hosts in the early going but lost their focus when the Thais scored twice — the first on a through pass by Sutee Suksomkit to Sarayoot Chaikamdee in the 15th minute and on Pipat Thonkanya, who helped himself to another through ball six minutes later.
"We were on equal footing with the Thais in the first 15 minutes of the game. But when we lost the first two goals, that changed the situation," said RP team coach Jose Ariston Caslib. "Our mentality is not on par with the Thai team. We tried to adjust in the second half and again we did well for a long spell but they overpowered us in the last 10 minutes."
The RP XI had a couple of chances to score in the second half but Christopher Greatwich missed on both occasions.
The Philippines also took a 0-4 beating from Malaysia in the opener Friday.
With back-to-back setbacks, the Filipinos dropped out of the semis race, leaving the chase for the top two berths among Malaysia, Thailand and Myanmar.