The weekend floating market along the Wat Sothon riverfront is worth timing your stay around if you have any flexibility - Saturday and Sunday mornings, early, before the day heat builds and before whatever crowds do appear. The food stalls along the river serve things you won't find in Bangkok tourist markets because nobody here is calibrating the menu for foreign tastes, and that difference is immediately obvious and immediately worth it. Ask staff specifically which stalls are currently good rather than just wandering - they eat there and have opinions.
Wat Sothon is worth visiting twice if you're here for several days - once on arrival to orient yourself, once early on a weekday morning when the pilgrimage activity is happening and the atmosphere is completely different from a daytime tourist visit. The merit-making around the main Buddha image on a quiet morning is genuinely moving in a way that's difficult to anticipate if your main temple reference point is the managed visitor experience at Bangkok's major sites.
Heat management in this part of Thailand matters more than it does in the north or on the coast where there's usually a breeze - the central plains in March through May can be seriously hot with limited relief, and structuring the day around an early start, a midday retreat to the pool or room, and a late afternoon return to activity is not laziness but the correct approach. The resort's pool and garden are specifically good for that midday hour when being anywhere else feels like a bad decision.
Bangkok day trip from here is realistic and some guests do it - the train back to Hua Lamphong, a day in the city, train back in the evening - but it requires energy and the honest truth is that most guests who come to Chachoengsao specifically to slow down find that a Bangkok day trip is the wrong instinct once they've been at the resort for 24 hours. The city will still be there. The garden and the quiet won't follow you back to it.
If you're visiting between October and December when the rains have ended and the countryside is at its greenest, the drive through the province in any direction is genuinely beautiful in a flat tropical way that photographs can't quite capture - the light through the rice fields in the morning at that time of year is a specific thing that people who've seen it describe with a specificity that should tell you something about what it actually looks like.