participating in local life by helping, for example, on a farm
What’s your level of Thai? Intermediate? Good? Excellent? Don’t expect farmers to speak anything other than Thai—or even Northern Thai in the north or Lao in the northeast. There’s a big difference between having a 5-minute conversation mostly with hand gestures during a brief encounter, like with a shopkeeper or a curious kid, and living and working 24/7 with a local family.
Anyway, this isn’t a common tourist activity in Thailand, even if you might find scam websites online ready to connect you with the "deep population" for a price 5 or 10 times higher than the real cost.
Also, in Thailand, any work (no matter what you call it), including volunteer work, even short-term, done during a tourist stay is illegal.
I’d like to meet the local people and take part in local life
You don’t need (and it’s complicated) to participate. Living a few days at the pace of an isolated village, even without speaking the language, will already give you a lot. It’s a great way to meet the local people, both in the village itself and during walks or bike rides in the surrounding countryside. However, if you want the place to be far from tourism, don’t expect any major sites to visit nearby. Does this approach work for you? If so, suggestions for villages in a nice setting can be included in a route proposal.
I was thinking of 29 nights on-site to simplify visa matters.
OK. It’s not a visa but just a stamp called "Visa Exemption" in your passport.
and beaches
How many of the 29 nights (including arrival/departure days) would you spend at the beach? 6? 7? Fewer?
Once you answer the two questions above, a route suggestion will be possible.
For now, and if I understood correctly (if not, correct me or add details), your criteria are:
- Countryside, mountains, and beaches
- Few or no other tourists
- Authenticity
- A slow, contemplative travel pace
- No domestic flights
November is rice harvest season.
Photos of the countryside and its inhabitants here:
https://voyageforum.com/forum/parties-campagne-thailandaise-d10760313/