In other matches of the day, the Netherlands defeated Uganda by seven wickets, tournament top seed United Arab Emirates (UAE) recorded a comfortable 102-run victory over Nepal, and Hong Kong defeated Scotland by 17 runs.
At Pukekura Park, New Plymouth, Vala (105 not out) and Siaka (103) put on a 154-run second-wicket partnership to lead PNG to victory over Kenya with 7.1 overs and eight wickets to spare.
It was a day for the batsmen at New Plymouth, with three centuries being scored. Kenya's Collins Obuya (106) set the tone, bringing up his century with a six over long off. PNG's Siaka (103) followed suit with a six to bring up his century from 80 balls, and man of the match Vala (105 not out) hit a straight six to get into three figures.
Twenty-one-year-old Siaka struck 11 boundaries and four sixes to reach 103 from only 83 deliveries, while Vala crafted an unbeaten 105 from just 109 balls (8x4, 6x6) to star in PNG's win.
Earlier, Kenya reached 249 for nine from its 50 overs, with Raymond Haoda (four for 50) and Pipi Raho (two for 47) being the leading wicket takers for PNG.
At Bay Oval, Mount Maunganui, Tauranga, North Island: Uganda 152 all out, 46.1 overs (Roger Mukasa 44, Abram Mutyagaba 36; Michael Rippon 4-15, Michael Swart 2-28, Mudassar Bukhari 2-30) vs Netherlands 155 for three, 30.1 overs (Wesley Barresi 61 not out, Peter Borren 50).
Result: Netherlands won by seven wickets.
At Pukekura Park, New Plymouth, North Island: Kenya 249 for nine, 50 overs (Collins Obuya 106, Rakep Patel 24, Maurice Ouma 24, Thomas Odoyo 42 not out; Raymond Haoda 4-50, Pipi Raho 2-47) vs PNG 250 for two, 42.5 overs (Assad Vala 105 not out, Lega Siaka 103, Chris Amini 28).
Result: PNG won by eight wickets.
At Rangiora Oval, Christchurch, South Island: UAE 297 for eight, 50 overs (Shaiman Anwar 109, Swapnil Patil 74, Salman Faris 35; Basant Regmi 3-43, Jitendra Mukhiya 2-58) vs Nepal 195 all out, 48.1 overs (Sharad Vesawkar 54, Shakti Gauchan 37 not out, Binod Bhandari 37; Kamran Shazad 3-46, Khurram Khan 2-19, Manjula Guruge 2-25, Amjad Javed 2-44).
Result: UAE won by 102 runs.
At Queenstown Events Centre, Queenstown, South Island: Hong Kong 263 for seven, 50 overs (Irfan Ahmed 75, Tanwir Afzal 42, Mark Chapman 36, Babar Hayat 31, Jamie Atkinson 27, Aizaz Khan 22 not out; Iain Wardlaw 3-57, Matt Machan 2-37) vs Scotland 246 all out, 48.4 overs (Preston Mommsen 118, Matt Machan 34, Rob Taylor 28; Nadeem Ahmed 4-37, Haseeb Amjad 3-53).
Result: Hong Kong won by 17 runs.
--IANS (Posted on 13-01-2014)