If you are starting from the airport, allow roughly 45–75 minutes by taxi or airport rail link plus MRT/taxi, depending on traffic; leave plenty of buffer for this being a layover. Begin at Wat Pho, ideally around 1:00 p.m. The temple is generally open until about 6:30 p.m., with admission around ฿300. Spend an hour seeing the enormous Reclining Buddha and wandering among the tiled chedis and quiet courtyards. Dress modestly—shoulders and knees covered—and remove shoes before entering temple buildings. The Grand Palace is a short walk north along Maha Rat Road; allow about 1½ hours and expect admission around ฿500. It usually closes in the late afternoon, so enter well before 3:00 p.m.; security is strict, and covered clothing is required.
From the palace area, walk to Tha Tien Pier and take the short cross-river ferry to Wat Arun, usually only a few baht and just minutes on the water. The temple is typically open until around 6:00 p.m.; give yourself an hour to climb the lower sections of the central prang and admire the detailed porcelain mosaic. The riverside light is especially attractive later in the afternoon, but don’t linger too long if your flight is the same evening. Return by ferry and take a metered taxi or tuk-tuk toward Thip Samai on Maha Chai Road—allow 15–25 minutes depending on traffic. Its famous pad thai costs roughly ฿150–400 per person; queues are common, so an early dinner around 5:00 p.m. is much easier than arriving at peak dinner time.
After dinner, Khao San Road is about a 10-minute walk from Thip Samai. Spend an hour browsing snack stalls, inexpensive souvenirs, cafés, and the surrounding lanes of Banglamphu rather than treating the main strip as the whole neighborhood. It becomes livelier after sunset, but keep bags and phones secure in the crowds. For an international flight, leave this area at least 3½–4 hours before departure: a taxi to Suvarnabhumi Airport can take 45–90 minutes in evening traffic, while Don Mueang is often 30–60 minutes but still unpredictable. If you have checked luggage stored at the airport, make the airport your final stop; otherwise, confirm luggage-storage hours before heading into central Bangkok.