Samui is large enough that the beach you choose shapes the trip. Chaweng has the densest services and nightlife, Lamai is active on a smaller scale, Bo Phut mixes beach time with the old fishing-village area, and the west and south coasts are quieter but more transport-dependent.
Chaweng suits travellers who want restaurants, shops and late evenings close together. Lamai offers a similar beach-town format with less intensity, while Taling Ngam and other outlying shores trade convenience for space and sunsets.
Road distances look short on a map but island traffic and indirect routes add time. Confirm the fare before a taxi or local ride, and choose accommodation within walking distance of the places you expect to use most.
Ang Thong Marine Park is a separate boat day rather than a quick beach stop. Departures and itineraries depend on sea conditions, so leave room to move the trip and ask the operator about transfers, landing fees and swimming expectations.
Samui also supports diving, cooking, yoga and Muay Thai activities. Beach flags and operator warnings matter: a calm-looking shoreline is not proof that swimming or a crossing is safe.