2 tailors in Phu Quoc, each with the prices people actually paid, how long the order took, and the honest notes from their reviews.

Phu Quoc has around 3 tailor shops, 2 of them profiled here from what their customers wrote. Prices depend mostly on the fabric you choose, so ask for the total with fabric included before measurements. The local strengths are suits, shirts, silk, linen and cotton.
Trần Hưng Đạo is the tailoring street — 1 shop line it — with more clustered on Số 89 đường 30/04 (1). Everything is within a short walk, so it's easy to visit two or three shops, feel the fabrics and compare quotes in one afternoon before ordering.
Read the recent low reviews before the star rating: a 4.8 with a fresh run of sizing complaints tells you more than the number. Agree the full price and the payment split before anyone takes measurements, order on your first day in town, and say what feels off at the fitting — that's where a good shop earns its reputation. The busiest names in Phu Quoc are Shop Cát Cát- VietNamSilk and Thành Danh Tailor; the smaller shops often win on attention.
Customers in Phu Quoc rarely put a number in their reviews, so treat any figure you are quoted as the starting point rather than the going rate. The fabric decides most of the bill, far more than the shop you pick, so ask for the total with the fabric you actually want before anyone reaches for the tape measure. Prices across Vietnam, city by city puts these numbers in context.
One of the 2 shops profiled in Phu Quoc routinely delivers in 24 to 48 hours, so the safe plan is two days: measurements and fabric on day one, a fitting the next morning, small adjustments and pickup that afternoon. Add a day for a three-piece, a wedding outfit or hand embroidery, and another if you want a second fitting.
Hoi An has hundreds of tailors in one walkable old town and turns most orders around in two or three days, and it is where the trade learned to work with travelers. Phu Quoc has 2 profiled shops, fewer options to compare in an afternoon though one of them still delivers in 24–48 hours. If Hoi An is on your route and you have two spare days there, order there. If it is not, or you are already here and the fit matters more than the choice of fabrics, the shops below do the same work — read the recent low reviews first and agree the price in writing. See what Hoi An offers.
Around 3 tailor shops, from one-room family workshops to big showrooms. 2 of them are profiled here from what their customers wrote, and more are added regularly.
Trần Hưng Đạo has the biggest concentration (1 shop), followed by Số 89 đường 30/04. They're all within walking distance of each other.
Hoi An has far more shops in walking distance and the fastest turnarounds in the country, so if it is on your route it is the easier choice. Phu Quoc works when you are already here: 2 profiled shops, fewer options to compare but the same craft.
Yes, and it is the most reliable way to get the fit you want: bring the garment that already fits you, or a clear photo of the cut. Reviews across these shops rate copying highly, more highly than describing a design from scratch.
Plan two to three days: first fitting within 24 hours, adjustments the next day. 1 of the shops here routinely finish standard orders in 24–48 hours.