Given significant visitor numbers from Malaysia, Indonesia and the Middle East, Phuket has a reasonably developed halal food scene.
Halal-certified restaurants
A number of restaurants across the main tourist areas carry official halal certification, displayed visibly — worth looking for the certification mark directly rather than assuming a restaurant is halal based on serving mostly Muslim-majority-country cuisine.
Where it's easiest to find
Phuket Town, with its historic Muslim community, and areas with higher Malaysian and Middle Eastern visitor numbers tend to have a stronger concentration of halal options than smaller beach-town strips.
Halal-friendly vs halal-certified
Some restaurants describe themselves as "halal-friendly" (no pork or alcohol used) without full certification — a meaningful distinction for travellers with strict requirements, worth clarifying directly with staff if certification matters to you specifically.
Self-catering option
Larger supermarkets stock halal-certified packaged goods and meat in the main tourist areas, useful for anyone self-catering in a villa or condo.