Hmm...now that you say that, I can hear the similarities in singing style between the two voices. However, Nantida has a deeper voice so I don't know if she sang "Hark Roo Suk Nid," or perhaps she sang at a higher pitch for all I know. Although, the one who sang the opening theme for Ban Sai Thong does sound a lot like Nantida...hmm... I wonder why no one knows who the singer is. I've tried searching in youtube using the Thai title (หากรู้สักนิด), but no artist comes up only the title of the song; it's so frustrating!