Eight people, six flights, one villa. The hard part was never the party - it's getting everyone in the same place with a boat waiting. Tell me the headcount and I'll handle the rest.

Thailand does loud and it does civil, and a good week has both. The trick is knowing which city does which, and not spending the one big night in the wrong place.
Alcohol sales stop nationwide on a handful of Buddhist holidays and election days. It has ruined more than one big night - send me your dates and I'll check them against the list before anything is booked.
Flat seas, 30°C, no rain. Also the priciest - villas for 8+ go months out.
36°C and humid. Rates drop, boats still run. Songkran in mid-April is a nationwide water fight - go for it or avoid it deliberately.
Short afternoon downpours, then sun. Half the price and half the crowds. Andaman seas get choppy; the Samui side is calmer.
The one window I'd push you off. Island days get called off at short notice and there's no second attempt in five nights.
Thailand ended visa-free entry for Indian passports. For a group, the e-Visa is the only sane route - one file per person, done before you fly, no cash counter at 2am.