Pool legend Efren Reyes, who was expected to make his much-anticipated comeback, was unable to make the nineball tournament with his teammate Carlo Biado due to travel issues.
As a result, the Philippines have been replaced by Thailand, with Un-Nooh and Saengkham stepping in at the very last moment.
The event gets underway on Tuesday, with defending champions Germany kicking off proceedings against New Zealand.
Thailand won't be in action until Thursday, which gives the snooker duo a couple of days to prepare before their clash against South Africa.
Un-Nooh, a World Snooker Tour ranking winner, and Saengkham, who reached the Last 16 of this year's World Snooker Championship, will take on the team of Jason Theron and Kyle Akaloo in a race to seven frames.
As a result of the change, the match between the Netherlands and Morocco was moved to the afternoon session on Wednesday. This also sees Poland's match with Hong Kong, China, and Greece vs Cyprus move forwards on that same day.
Some of the world's best players are involved in the 15th edition of the World Cup of Pool which is being held at the Brentwood Centre in Essex.
Defending champions Germany, for instance, are represented by the recent winner of the UK Championship Joshua Filler and his teammate Thorsten Hohmann.
The United States, on the other hand, have pool royalty Shane Van Boening and his Mosconi Cup compatriot Skyler Woodward.
Great Britain, meanwhile, have two teams on show, with Jayson Shaw and Elliott Sanderson making up the first. Imran Majid and Chris Melling will represent Great Britain B.
Mika Immonen, Albin Ouschan, David Alcaide and Niels Feijen are also among the star-studded field for what promises to be an enthralling event.