The report, which ranks 143 countries and territories, saw Vietnam rise from its 54th position in 2023 to 46th globally. Vietnam was also noted to be among the top gainers this year, alongside China, Mongolia, and the Philippines in Asia.
Finland was crowned the world's happiest nation for the eighth consecutive year.
Nordic countries dominated the top ranks, with Denmark, Iceland and Sweden joining Finland in the top four. European nations generally performed well, occupying most of the top 20 spots.
Israel, despite ongoing conflict with Hamas in Gaza, ranked eighth. Costa Rica and Mexico broke into the top 10 for the first time, securing sixth and tenth places, respectively.
In contrast, the US fell to its lowest-ever ranking of 24th, with the report highlighting a 53 per cent increase in the number of Americans dining alone over the past two decades.
At the bottom of the list, Afghanistan remained the least happy country, followed by Sierra Leone and Lebanon.
The rankings are based on self-assessments of life satisfaction by residents, published by the Wellbeing Research Centre at the University of Oxford, in partnership with Gallup, the UN Sustainable Development Solutions Network and an independent editorial board.
Researchers identified key factors influencing happiness, including health, wealth, and seemingly simple elements like sharing meals, having trusted social support and household size.
Trust in others' kindness also correlated strongly with happiness, with those believing in the return of a lost wallet reporting higher life satisfaction./.