Check into your centrally located hotel (Sukhumvit or Silom) and refresh — choose a place near nightlife (Thonglor/RCA/Khao San) for easy late-night returns.
Wander markets, temples and food stalls; great for street-food sampling and interesting offbeat temples — busiest and most lively in the afternoon/evening.
Thailand allows licensed cannabis sales at registered shops — visit a reputable dispensary in Sukhumvit/Thonglor and consume only in permitted private venues; public smoking is illegal, so check rules and ID requirements.
Visit the Grand Palace (open 8:30–15:30) and nearby Wat Pho (8:00–18:30) to see Thai royal and temple architecture; dress respectfully (no shorts or sleeveless shirts).
Take a 30–45 minute speedboat/ferry to Koh Larn for clear water, snorkeling and beach clubs; boats run frequently and return trips through late afternoon.
If the 'Hangover Hotel' experience or pop-up themed bars are running, this is a great night to visit; many of these are rotating concepts — check current listings and book ahead.
If this date falls on a weekend, explore Chatuchak (9:00–18:00) for offbeat shopping and local snacks; if weekday, visit JJ Green or local malls and markets.
Thailand currently has no legal land-based casinos for locals; the nearest legal casinos are across the border in Cambodia (Poipet) and require a separate overnight border run (3.5–4 hours each way from Bangkok plus immigration). If a casino night is essential, consider swapping a Bangkok night for a quick Poipet overnight (plan passport, visas, and time).
Depart early for a Phi Phi highlights tour (snorkeling, Maya Bay viewpoint, Monkey Beach, Viking Cave); most tours run ~07:00–16:00 and include lunch and snorkel gear.