Plaek Phibunsongkhram
Strictly speaking, Subhas Chandra Bose was present only as an "observer", since India was a British colony. Furthermore, the Kingdom of Thailand sent Prince Wan Waithayakon in place of prime minister Plaek Phibunsongkhram to emphasize that Thailand was not a country under Japanese domination. He was also worried that he might be ousted should he leave Bangkok.