I have finally found this song today - about five years after watching it in the hotel room while holidaying in Hat Yai, Songkhla, Thailand.
I find the music very moving but I have no ways to search for it online since I could neither read nor write Thai.
Despite not understanding the lyrics, I could somehow associate it as a song about the Thai King judging from the images shown on TV.












The British army surrendered Singapore to the Japanese forces at the Ford Factory in Bukit Timah on 15 February 1942.




