Although I could make it in one day from Pattaya to Chiang Mai, I would rather take it more leisurely and stop off somewhere interesting en route.

Ditto the return journey from Chiang Rai to Pattaya.

Does anyone have any recommendations for good places for stopovers?

I will have my daughter and her boyfriend from UK, plus wife, traveling with me.

Something scenic/cultural would be good.

Thanks folks

Mobi

Depending on which routes you are intending the list of places to stop is endless..

Assuming you are taking the up via route 1 asia highway, and then back down through Isaan 'loop' i would break off this monotonous drive with intermissions at beung boraphet (largest freshwater lake in Thailand, just outside Nakhon Sawan) and an overnight tented (everything can be rented from the HQ) stay at Nam Nao National Park near Khoen Kaen.

Sukhothai has bags of culture and defo worth a look if you've never been before and one has visitors. Come off the main route at Phitsanulok and head northwest - roughly 2/3 way between Bangkok and CM. Original capital with stunning old temple architecture, much like Ayuthaya but all in one area. Si-Satchanalai Park, about 50kms north of here, is even more impressive and serene IMO and tickets for Sukhothai also cover entry to Si-Satchanalai, last time I was there. Should be possible to get back over to the main highway from here.

Note. The attraction in Sukhothai is the historical park and not the town itself which is much like any other Thai town and a bit of a nonentity. Some good guesthouses and restaurants though.

Sukhothai and Beung Boraphet at Nakhon Sawan seem good candidates for the outward journey.

It's a good idea to swing by Issan on the way back.

Any recommendations for a stop overs in Issan?

BTW the tent idea sound good, but i'm not sure I could mange that at my age and current state of health.