Hi there. We have just over 2 weeks in Thailand next March and are figuring out our itinerary.

We will arrive into Bangkok and likely leave via Bangkok too (moving onwards to Ho Chi Minh)

We want to spend and good amount of time eating our way around Bangkok and seeing some of the country, but value seeing a few places properly rather than rushing through a dozen destinations. We're mostly interested in food, art, culture and scenery. For this trip, we're looking just at Central and Northern Thailand and will save the Southern Islands for another time.

At the moment our rough itinerary is:

3 nights - Bangkok

1 Night - sleeper train from Bangkok to Chiang Mai

2 nights - Chiang Mai

1 night - Chiang Rai

1 night - back in Chiang Mai

2 nights - Pai

1 night - back in Chiang Mai before travelling back to Bangkok, either by train/bus/plane (undecided!)

2/3 nights - Bangkok

Does this seem doable and/or like a good overview?

I wonder if it's preferable, as an alternative, to skip Chiang Rai, and instead spend the time visiting Ayutthaya and/or Lopburi en route to/from Bangkok. Thoughts?

In March, you may run into the smoke from burning fields in Northern Thailand. If you do, the whole area will be pretty unpleasant.

As Kathie says, there is a possibility, indeed probability, of severe pollution due to the burning of the fields and forest. We have visited a couple of times in March and regretted it. Either change the time of your visit to end mid Feb at the latest or choose somewhere other than the north of Thailand.

Ayuthaya, kanchanaburi, Lopburi should be ok. We also enjoyed Nan a lot but again it is probably too far north.