Ong Beng Seng’s shirt is from Thom Browne
It turns out, Ong's choice of men's wear is from the "Thom Browne" label, which is known for pieces that feature a distinctive striped design on the pockets or sleeves, as well as the occasional visible label attached to the shirt's bottom, on the front left. Ong's choice of top on Friday was most likely the "Thom Browne Blue Flared Collar Shirt".