With no explanation, label text_A→text_B with either "DON'T KNOW", "NO" or "YES".
text_A: The Viet Cong Russian roulette scenes were shot with real rats and mosquitoes, as the three principals (De Niro, Walken, and Savage) were tied up in bamboo cages erected along the River Kwai. The woman who was given the task of casting the extras in Thailand had much difficulty finding a local to play the vicious-looking individual who runs the game. The first actor hired turned out to be incapable of slapping De Niro in the face. The casting agent then found a local Thai man, Somsak Sengvilai, who held a particular fondness of Americans, and so cast him. De Niro suggested that Walken be slapped by one of the guards without any warning. The reaction on Walken's face was genuine. Producer Deeley has said that Cimino shot the brutal Vietcong Russian roulette scenes brilliantly and more efficiently than any other part of the film.
text_B: Did Somsak Sengvilai probably feel bad about having to slap the actors?
YES.