The video, which features Salman Khan and Kareena Kapoor, has had over a million hits on YouTube.
King spoke to Digital Spy about how he became involved in the Pritam-composed soundtrack.
"I was in Kolkata with my dad and I got a call from Pritam, as he heard I was there from a mutual friend," said the singer. "He then flew me over to Mumbai and I was in the studio as soon as I landed recording 'I Love You'."
King had earlier recorded the songs 'Te Amo' for Dum Maaro Dum and 'Suno Aisha' from Sonam Kapoor vehicle Aisha.
The Southall-based musician said: "After the success of my last song 'Te Amo' I felt pressured by the release of this song, but at the same time I knew I needed another song out there which could showcase my voice.
"So when the song was picked for the film and released on the first promo I was very happy."
King revealed that although a well-known playback singer had recorded a version of 'I Love You', lead actor Khan had personally opted for his version.
"The stylist for the film recently visited London and told me he was actually there when Salman heard my version of the song and chose it for the film," King said.
"I'm very grateful to him and the team for choosing my version and have just heard it's gone to number one on the Asian music charts as well."
Bodyguard, Khan and Kapoor's third film together, releases worldwide on August 31.
Watch the video for Ash King's 'I Love You' below: