Just got back from Railay and want to provide some feedback on the tailor at Railay as I couldn't find any information myself on TripAdvisor. There are 2 tailors on Railay- one on Walking Street and one on the East side, south of Railay Bay Resort, however they are actually the same company, so just go to the one on Walking Street as it's a bit bigger.
I initially ordered 3 shirts as I am a weird body shape, which I got for 4000 baht (under $150 AUD) which I was happy with. So I asked (and eventually) ordered a suit also for 7000 baht (jacket + 2 pants). Prices do vary based on material.
I haven't worn the suit yet, but the cut, finish and sizing is great- I am very happy with it. They were professional, taking a wide range of measurements over 3 fittings- first measure, 2nd measure with first cut of material and then final fitting. Turnaround time was great also- I was measured for my suit first thing in the morning and had 2nd measure that evening.
Opening hours- 10am to 10pm (ish). I'd say more like 10.30am to 9pm.