Start early at Wat Arun (Temple of Dawn), ideally by 7:00–8:00 AM, before the tour buses and the heat kick in. It’s one of those Bangkok mornings that actually feels calm if you arrive early: the river air is softer, the porcelain towers catch the light beautifully, and you can wander the grounds in about 1.5 hours. Entry is usually around 100 THB, and the easiest way in is by crossing over on the little Chao Phraya River ferry from Tha Tien Pier. Wear something modest because it’s an active temple, and if you want photos without crowds, circle the base first and then head up once the light is right.
Walk or take a very short boat hop to The Deck by Arun Residence for lunch with a front-row view of Wat Arun across the water. This is one of the nicest places in Bangkok Yai to sit down, cool off, and actually look back at where you just were. Expect around 500–900 THB per person depending on what you order; reservations help if you’re going at peak lunch time. It’s a good reset before the historic-core temple circuit, and you can take your time here—there’s no need to rush.
After lunch, head to The Grand Palace in Phra Nakhon; from the river side, a taxi or tuk-tuk is simplest, usually 10–20 minutes depending on traffic. Plan for about 2 hours, and know that admission is typically around 500 THB. This is the big one: dress correctly, expect security and walking, and don’t be surprised if it feels busy even on a weekday. From there, it’s an easy short walk to Wat Phra Chetuphon (Wat Pho), where the pace softens again. The reclining Buddha is the headline, but the shaded courtyards and quiet corners are what make the visit feel restorative; budget another 1.5 hours and about 300 THB for entry.
Finish at Thipsamai in Old Town / Phra Nakhon for an iconic Bangkok pad thai dinner. Go a little before the real dinner rush if you want to avoid the longest queue; even then, the line usually moves fast, and a meal is typically 150–300 THB. It’s a very practical end to the day because you’re already in the historic district, and you can keep the evening loose afterward—either stroll around the old streets a bit or just head back by taxi. If you’re going home later, leave around 7:30–8:30 PM to beat the heavier traffic and make the most of the cool night air.