Worth getting out of bed for
The Siam's intimate Opium Spa by Sodashi is a must for pleasure hounds, drawing on all-natural products inspired by the earth and sea. Choose between solo or couple's suites with steam rooms, saunas and Jacuzzis. Chill out in the hammam-style Bath House, then retire to the relaxation space. Facials, body therapies, massage, mani/pedis and wellbeing programmes are all up for grabs. The Kids' and Teen Menu is a cute touch, and there are specific pampering perks for men.
It's not often that hotel gyms tick the good-looking box, but the Siam's is spacious and serene, overlooking a monastery, with personal trainers on tap. Unwind on the outdoor yoga terrace, try t'ai chi or get fighting fit in the muay Thai ring (the spa offers a Muay Thai Recovery package if you overdo it). Training options abound for beginners or experienced boxers, and the chef can even tailor your diet to match.
More in the mood for creating your own Thai food? The smart cooking school, under Chon Thai Restaurant, hosts daily classes on request, which begin with a market tour led by the chef (sessions run from 9.30am to 12.30pm or 2.30pm to 5.30pm).
For cultural highs, ogle hand-picked curios and antiques in the hotel's cabinets and inviting library (home to owner Krissada Clapp's collection of rare, first-edition hardbacks on old Siam and Asia and his mother Kamala's neolithic pottery pieces).
You're just five minutes from the Vimanmek Teak Mansion and child-pleasing Dusit Zoo, both in Dusit Park, and 15 minutes from the National Museum, Grand Palace, and mesmerising temples Wat Pho and Wat Arun downstream. Make the most of the Siam's free speedboat for whizzing to riverside sites, or let the concierge hook you up with an in-the-know private guide. Smith also recommends checking out the floating markets and sleepy scenes on the city's smaller khlongs (canals), easily expored by longtail boat. Fans of muay Thai can watch the real thing at nearby Ratchadamnoen Stadium.
Further afield to the north, the Chatuchak Weekend Market is worth a visit, with hundreds of stalls toting clothing, handicrafts, homewares, food and pets (live snakes, anyone?). The shopping-averse can content themselves with Curio, the Siam's small boutique, which offers an elegant edit of accessories, from travel posters to jewellery, antiques and toiletries.
For a fantastic local experience near the hotel in Thewit, head for Krua Apsorn (+66 (0)2 241 8528; www.kruaapsorn.com) at 503–505 Samsen Road, a cosy dining room which has served members of the Thai royal family and bagged press plaudits. Crab, shrimp, snapper and mussels star in a range of tasty curries and stir-fries for lunch or early supper, backed up by soups, papaya salad and coconut ice-cream. Another good bet nearby is Rosabieng Restaurant (+66 (0)22 53 5868), at 3 Sukhumvit soi 11, which serves delicious Thai food and cool beers on the terrace.
Stick with the Siam's musical theme by popping out for a drink at neighbourhood jazz bar Brown Sugar (+66 (0)89 499 1378; www.brownsugarbangkok.com), at 469 Phrasumen Road. It's open in the day for coffee or lunch, with drinks and live music nightly until the wee hours.
Phra Athit Road, just south of Dusit near the Chao Phraya River, is a charming spot with a host of hip cafés, bars and restaurants set in beautiful old shophouses.
Come evening, make time for a movie in the atmospheric screening room off the lobby, equipped with classic folding wood-and-velvet French cinema seats. The space also screens Thai history clips and hosts guest speakers.