The two officially wed in France in August, but waited until Saturday to celebrate in their home country at the Kampong National Tropical Botanical Gardens, People magazine reported.
The two were spotted aboard a boat called "Never Say Never" while wearing tartan plaid outfits just before exchanging vows.
Pharrell and Lasichanh have been together for five years and have one son, Rocket, 4.
Williams told the "Today" show in August his relationship is "awesome."
"The bestie thing is awesome. Every night is like a sleepover," he said.
Costly malfunction causes beer flood at Boston-area brewery
Wisconsin business offering 'therapeutic cuddling' forced to close