Do not do three themes in one day
A first visit plans two things, and both have to be walkable back. The walls plus Wat Pho are one. Wat Arun is the second, across the river, and then you stop. Chatuchak takes a weekend day. Thonglor is an evening lane. Four of these in one day leaves you matching receipts on a train. Who splits them: anyone staying more than four days gives the market, Thonglor and the west bank each their own half-day.
Split the transit
Split the tickets before you leave the hotel. The BTS uses Rabbit: the official FAQ lists a standard card at 200 baht, of which 100 is the issue fee and 100 is usable value. From 1 June 2026 the Blue Line stopped the old MRT stored-value card and uses EMV contactless bank cards, which are still not Rabbit. The airport line is another system; a government page says the Express service is suspended. The Chao Phraya orange line is the express commuter boat (from 6 October 2026, 19 baht flat on weekdays). The tourist boat is another company. The Saen Saep boat is another line again. Do not reuse an old guide's 120-baht day pass, and this station does not freeze a day-pass price.